South Korea on Tuesday reported its first deaths from an outbreak of the MERS virus that has infected 25 people, caused widespread alarm and triggered a closer watch by Asian neighbors on Korean arrivals.

South Korea on Tuesday reported its first deaths from an outbreak of the MERS virus that has infected 25 people, caused widespread alarm and triggered a closer watch by Asian neighbors on Korean arrivals.

The two deaths were only the second case of fatalities from MERS (Middle East Respiratory Syndrome) in Asia since a man died in Malaysia in April 2014.

In China state media said hundreds of people had cancelled trips to South Korea, while Thailand and Vietnam said they were reinforcing monitoring of inbound passengers at airports.

Hong Kong also stepped up surveillance and placed 18 people who had been seated near an infected Korean man on a flight from Seoul last week under mandatory quarantine.

The deaths announced by the South Korean health ministry were of a 58-year-old woman and a 71-year-old man.

Six more people were diagnosed with the MERS virus Monday night, the ministry said, bringing the total number of people infected to 25 including the two deceased.

The first case -- a 68-year-old man diagnosed after returning from a trip to Saudi Arabia -- was reported on May 20.

Around 750 people who were exposed directly or indirectly to the virus have now been placed under varying levels of quarantine.