A woman was killed and three people, including a 2-1/2-year-old boy, were hurt in another indiscriminate attack in Beijing yesterday amid rising concerns over public safety on the mainland.

A petitioner in a wheelchair set off a home-made bomb near the international arrivals gate at Beijing Capital International Airport yesterday evening, raising security concerns at one of the world's busiest airports.

"My brother was so miserable with his injustices, and now, we don't know where he is and what he was arrested for," Ji Zhongji, elder brother of bomber Ji Zhongxing, told the Post yesterday.

Messages of support posted online came after reports said 34-year old Ji Zhongxing was driven to the act by a years-long battle for justice after being severely beaten by police.

Security officials in the Guangdong city of Dongguan have been ordered to reopen the case into an alleged beating eight years ago that paralysed a motorcycle taxi driver who set off a home-made bomb in protest at Beijing's airport on Saturday.

Some mainland airports have ramped up security checks after a home-made bomb was set off at Beijing Capital International Airport at the weekend, but the government denied that the new measures were linked to the small blast.