One of the first things political cartoonist Wang Liming did last month after being released from almost 20 hours of detention and questioning by Beijing police was to post a message online to his followers. "I am out," he wrote on mainland microblogging site Sina Weibo, before thanking his 300,000 fans for their support. "I have seen and heard many interesting things in the police station overnight," he continued, promising to share his experiences.

Within 24 hours, Wang had posted a series of pencil sketches that showed in detail how he had been questioned for "spreading rumours online and stirring trouble". His drawings depicted the cushioned walls and uncomfortable steel chair in the police interrogation room; the small, spartan cell in which he spent the night; his fear of being sexually molested by other inmates; and an SMS conversation a chatty policeman had shown him of an argument with his wife, who was threatening to divorce him for never being at home.

Fortunately, Wang told his followers, the police let him go with just a warning for reposting unverified messages on social media about unreported deaths of flood victims in typhoon-hit Zhejiang province.

This was not Wang's first brush with the law. He told Post Magazine in a telephone interview just three days before his latest detention that he had been "invited to tea" - a common euphemism for being detained, warned or threatened by the police or state security agents - on several occasions for his defiant speech and online artwork.

Better known by the alias "Rebel Pepper" and for his signature self-portrait - a flamboyant red chilli pepper with a sarcastic smile - 40-year-old Wang is a leading figure among an emerging group of political cartoonists who have established their voices and found increasing popularity on the mainland's social media networks, despite an intensifying campaign launched by the government this year to suppress dissent in cyberspace.

"They [the police] tried very hard to find out if my unruly comments online were propelled by a certain overseas anti-China force," Wang says. "But the expressions were made only out of my impulse to comment on current affairs."

Early last month, he posted a one-cell cartoon that became one of the year's most shared works of satire. In just 48 hours, the drawing had attracted more than 28,000 reposts and more than 5,000 comments on Weibo. It depicts a teenage boy, dressed in a Red Army uniform from the civil war in the 1930s, holding a spear and reprimanding a sheep and a wolf. "Now let's talk about the serious problem of your violent tendencies," says the boy. The background features a burning house and a faceless, bloody corpse.

As most viewers over the age of 35 would have known, the boy is a reference to the teenage hero in the "revolutionary" classic Shining Red Sta r, a film set during the civil war. In revenge for the mistreatment of his tenant parents, the film's protagonist kills a rural landlord and burns down his house. The crestfallen sheep and wolf, on the other hand, are more recent creations - the hero and villain of the wildly popular animated series Pleasant Sheep and Big, Big Wolf, which has dominated mainland television screens for the past eight years.

Most reposters regard Wang's work as a brilliant parody of a recent spate of editorials in state media attacking "excessive violence" in the animated series, which features a herd of cute young sheep and a clumsy grey wolf. "They shot all these ultra-violent 'revolutionary movies' over the years and now they have the audacity to criticise a couple of cartoon characters for violence? What an irony!" says one commentator.

Wang admits he considers censoring himself, however. "I simply do not want my account to be deleted again," he explains. His Weibo account has been deleted more than 200 times over the past few years, he says.

As with Twitter, if a Weibo account is deleted, the user loses every-thing that was on it (posts, photos, followers) and, if they want to re-join, they must register under a different user name. Bloggers who already have a certain degree of influence among supporters and fans, however, can quickly recover their followers. For example, friends who have many followers can be asked to advertise a poster's comeback in their own messages.

Recent news reports have given the public a glimpse into the official censorship operation imposed on China's largest microblog service.

"We saw a fairly sophisticated system, where human power is amplified by computer automation, capable of removing sensitive posts within minutes," reported a research team from Rice University, in Texas, in the United States, and the University of New Mexico, in March after it had studied the speed at which Weibo is censored.

Reuters reported in September that about 150 graduates, all male (women are said to shun the work, in part because of the offensive material they would have had to deal with), were employed to censor Sina Weibo day and night. Former staff told the news agency that cen-sors process about three million posts in an average 24-hour period, which means each must sift through at least 3,000 posts an hour.

"At first, I vented all my anger on Sina," says Wang. "But I can understand them [the censors] now, as I know they are not behind it."

News of his latest detention helped boost Wang's Sina Weibo following by 10 per cent. That is a welcome development, he says, because the purpose of sharing his work online is to enlighten and inspire audiences.

Kuang Biao, 46, is one of the few old-school cartoonists not only active on social networks, but also to have his work appear in a wide range of print publications. His is a familiar face at national cartoon competitions, after 30 years in the industry. In 2010, Guangzhou-based current affairs newspaper The Time Weekly selected him as one of the mainland's 10 most influential news workers.

Kuang adopts a traditional approach - he uses hard-tipped writing instruments to produce his creations. "That's what gives it power," says a fellow artist.

Currently working as a political cartoonist for the influential Southern Metropolis Daily - another Guangzhou-based newspaper, which is known for its liberal views - Kuang carefully chooses what he will post online from among those of his drawings newspapers decide not to run due to concerns about censorship.

Kuang said in a speech at the non-profit TEDxCanton conference in 2010 that the cartoon is a powerful medium because it can carry a veiled message: "In an environment that lacks freedom of speech, there is no room for blunt critical cartoons. This is predetermined by our domestic environment, or should I say, 'socialist' characteristics."

Kuang politely declined a telephone interview with Post Magazine because, he said, it would be taped. Instead, he answers questions via the popular messaging service QQ.

He says he is grateful to be working for a "benchmark" newspaper that does not interfere in his private creations. "But of course, I can enjoy myself just as much without the Daily. I am not worried about finding a shelter."

For Shanghai cartoonist and former animation producer Liu Jun, time is of the essence. The majority of his cartoons are inspired by breaking news. For example, he published a series of illustrations recently that lashed out at the mainland's shoddy medical-care system a day after a man reportedly cut off his own leg because he could not pay his medical bills. "Heated news often does not last more than a few days, so there are always new topics available for inspiration," says Liu.

Known as "Big Corpse Brother" online, Liu says his work mainly targets "vile practices and unjust behaviour in society".

"Cartoons are sometimes more powerful than text in evoking resonance and self-reflection among people," he says. "Cartoons are easy to understand, great for dissemination and thus a great medium for me to interact with online users."

Liu has more than 130,000 followers on Sina Weibo.

The medium, however, means much more to another enthusiast. "Drawing a cartoon is a process for me to conquer fear," says "Let's Draw David" from Shanghai, who declines to reveal his real name and asks instead to be called Pedro.

Pedro came up with his now well-known alias after he initiated artistic action online last year by asking users to draw a sculpture of "David". This was in response to a state television newscast that censored the private parts of the famous sculpture by Italian renaissance artist Michelangelo - a measure Pedro calls "ignorant and stupid".

His cartoons have a distinctive personal style. They are made up of just four colours - black, white, red and green - which, he says, represent darkness, hope, the Communist Party and the army, respectively. These four elements, he adds, represent the social phenomena that have inspired his work.

Pedro's blog,, features all of his cartoons and news updates. Earlier this year it won the best Chinese blog award from German international broadcaster Deutsche Welle "for its use of a humorous approach to comb [through] and present Chinese news".

When asked to comment on cartoonists in the mainland who self-censor, Pedro, who works as a kindergarten teacher in Australia, says: "I can understand, but not agree with them. Freedom of expression is never taken for granted. You fight for it … or you give it up for your enemy."

Although he says there is absolutely no self-censorship in his own work, Pedro expresses concern that his parents and friends at home might be subjected to harassment if his identity is revealed.

"Thus continues [the] creation of cartoons in defiance of the censorship. For me, [that is conquering] my fear little by little," he says.

"One day, when I can comfortably reveal my name, I will know I have completely conquered my fear. I hope that day will come soon."