“Travellers are also advised to take precautionary measures, wear a mask and observe hand hygiene when entering healthcare facilities and visiting overcrowded places.”

Watch: Asia's tourists avoiding Mers-hit South Korea

All Hong Kong tour groups to Korea this month – involving about 12,000 Hongkongers in 600 groups – will be cancelled after the warning was issued.

The decision came after representatives of 15 travel agencies met this morning to discuss contingency plans in the wake of the Mers outbreak.

Tourists can have all of their tour fees and airport departure tax refunded.

Acting Chief Executive Carrie Lam Cheng Yuet-ngor said security and health officials had been in talks with travel agencies to discuss the latest situation in Korea.

“The Security Bureau has agreed that if the issue of public health affects Hong Kong people’s health, [it] can use this travel alert system to issue a clearer message for the [travel] industry to follow,” she said.

Travel Industry Council executive director Joseph Tung Yao-chung said the alert helped travel agencies to better handle the situation.

He said some agencies had been left in confusion when the government yesterday issued health advice for travellers to Korea instead of a formal travel alert.

He said only a formal alert could help tour operators discuss partial refunds from airlines.

But cruise trips to Korea, such as to the coastal city of Busan some 325km from Seoul, would still go ahead. Tung said the decision on whether to cancel cruises lies with ship captains.

Counters at Hong Kong International Airport for two Korean flagship airlines appeared quiet this afternoon

Very few travellers were spotted as both an Asiana Airlines flight at 1.50pm and a Korean Air flight scheduled for 2.05pm prepared to depart for Seoul. Some airline staff wore surgical masks.

A Korean businessman who had been in Hong Kong for three days said he had been paying attention to the news of the Mers outbreak. 

"I am not worried about it. I have to go back home anyway," he said.

A tourist, who identified himself as Mr Ng, said he was flying to Seoul to connect to another flight to the US.

"If it wasn’t for the stopover, I would not go to Korea. The outbreak of the disease sounds uncontrollable," he said.

Ng said he would stay at the airport in Seoul for about an hour while catching his connecting flight and would wear a mask for protection.

Cathay Pacific meanwhile, has cancelled one of its five daily services to Seoul throughout July and August. Airline Route, a global flight database, said flight CX434/438 from Hong Kong (which departs at 7.55am or 8am on alternate days), and the return flight CX439 (1.35pm) from Seoul had been cancelled.

Elsewhere, Taiwanese carrier Eva Air will operate two flights a week through July on its Kaohsiung-Seoul service, down from seven. Subsidiary Uni Air’s planned twice-weekly service from Taichung to Seoul starting July 2 has been postponed until October 25. Selected Taipei-Seoul flights on Eva Air will be downgraded to smaller planes, while rival China Airlines has also adjusted Kaohsiung and Taichung services to Seoul.

About 25,000 people cancelled trips to South Korea from Friday to Sunday, the Korean Tourism Organisation said yesterday.

South Korean health authorities today announced that a 68-year-old woman had become the seventh fatality linked to Mers and reported eight new cases, raising the total number of infections to 95.

The announcement of the latest fatality came as Seoul vowed all-out efforts to contain any further spread of the potentially fatal respiratory disease since the first case was confirmed on May 20 – a 68-year-old South Korean man with a recent history of travel to four countries in the Middle East.

As of yesterday, more than 2,500 people have been quarantined while more than 1,900 schools, including kindergartens, have been temporarily closed.

Meanwhile, a joint team of eight South Korean experts and eight experts from the World Health Organisation began work today to assist efforts to fight the virus.

For five days, the joint mission will discuss infection control and epidemiological investigations into confirmed cases, visit hospitals that have confirmed cases or isolated patients and analyse the characteristics of the virus, according to the health ministry.

South Korea now has the second-largest number of Mers patients after Saudi Arabia, which has reported more than 1,000 confirmed cases since the virus emerged there for the first time in 2012.

Globally, since September 2012, the WHO has been notified of at least 1,185 laboratory-confirmed cases of infection with Mers, including at least 443 related deaths.

Meanwhile, Macau’s health chiefs followed Hong Kong in raising the travel guidance for South Korea to high-alert, the second biggest warning on a four-level scale. Officials in the gambling enclave recommended against travel unless absolutely necessary.

According to the Macau Daily Times the authorities are also trying to trace a Korean visitor who entered Macau after coming into contact with a Mers patient on a flight to Hong Kong. His whereabouts are still unknown.

Hong Kong’s “red” alert for South Korea is the first health-related security warning it has ever issued. The last “red” travel alert was issued for Nepal on April 27, following the massive earthquake there.

Hongkongers in Korea who need assistance can call the 24-hour hotline of the Assistance to Hong Kong Residents Unit of the Immigration Department at (852)1868 or contact the Chinese embassy’s consular protection hotline (82)10-97249110.