South Korea's health ministry reported on Monday two more deaths in the country's Middle East Respiratory Syndrome (MERS) outbreak, which the World Health Organization said was "large and complex," bringing the number of fatalities to 27.

Thailand, which reported its first case last week, said it had no new cases, raising hopes the virus there had been contained. Neighbouring Malaysia announced nonetheless that it was stepping up health screening at all entry points.

The outbreak in South Korea has been traced to a 68-year-old man who returned from a trip to the Middle East in early May and sought medical help at different hospitals before being diagnosed with the MERS virus.

The health ministry in Seoul also confirmed three new cases, taking the total to 172 in an outbreak that is the largest outside Saudi Arabia, but has shown signs of slowing credited to wide-reaching control measures.

MERS was first identified in humans in Saudi Arabia in 2012 and the majority of cases have been in the Middle East.

Isolated cases have cropped up in Asia before South Korea's outbreak began last month, and Thailand reported its first case last week in a 75-year-old man from Oman who had traveled to Bangkok for treatment for a heart condition.

"Today we can assure [you] that we have found no new MERS cases," Thai Deputy Health Minister Vachira Pengchan told a news conference.

"Overall we are able to control the virus and the risk is lower," Vachira said, adding that the condition of the lone MERS patient was improving.

MEDICAL TOURISM

Thailand is a popular hub for medical tourism, with around 1.4 million visitors traveling there for healthcare each year, and Vachira said the public health ministry might ask private hospitals treating foreign patients to screen those traveling from high risk areas, including South Korea and the Middle East.

Malaysia, which shares a 650 km (400 mile) land border with Thailand, has already begun monitoring passengers' body temperatures at its airports, Deputy Health Minister Hilmi Yahaya said in a statement to state news agency Bernama.

"Now, we are going further to include all entry points," he said.

South Korea's health ministry said last week that the outbreak may have leveled off, although it said more cases were expected. It reported no new cases on Saturday, the first time in 16 days.

The latest fatalities reported in South Korea on Monday were of patients aged in their 80s with pre-existing health problems, the health ministry said.

Most of the schools that had shut two weeks ago as fear grew about the possible spread of the virus outside hospitals were re-open on Monday, with just six remaining closed, according to the Education Ministry in Seoul.

The number of people who were in quarantine was also down to 3,833 as of Monday, a decline of 202 people from the previous day and down from a peak of more than 6,700 people last week.

All of the South Korean cases have been traced to hospitals.