South Korea has reported three new cases of Middle Eastern Respiratory Syndrome (MERS), bringing the total number of people infected to 169 in the largest outbreak outside of Saudi Arabia.

The country's health ministry also reported its 25th fatality on Sunday, after the death of a patient who also had a heart condition and diabetes.

Sunday's announcement came a day after the country reported no new cases, raising hopes that Seoul was winning the battle to contain the virus.

Infographic: The spread of MERS

Two of the cases newly diagnosed on Sunday involved medical workers, the AFP news agency reported.

They included a doctor who treated a MERS patient at Samsung Medical Center in Seoul, seen as the epicentre of the outbreak, where more than 80 people have been infected. The other medical worker had taken x-rays of a patient in another Seoul hospital.

A total of 43 people have so far recovered and have been released from hospital, including seven between Friday and Saturday, the ministry said.

Fourteen patients are in a critical condition, it said.

Fall in cases

The number of new patients had been falling for three straight days from eight on Tuesday to none on Saturday.

The number of people exposed to patients and quarantined at state facilities or at home also fell to 4,035 on Saturday from a peak of more than 6,700 on Wednesday.

The outbreak began on May 20 when a 68-year-old man was diagnosed after returning from a trip to Saudi Arabia.

Since then the virus has spread at a rapid pace, sparking public alarm that prompted the temporary closure of thousands of schools and trip cancellations by more than 120,000 foreign tourists.

Almost all patients were infected in hospitals and the World Health Organization (WHO) said it had found no evidence of transmission of the virus within communities outside hospitals.

WHO chief Margaret Chan said on Thursday that Seoul was now "on a very good footing" after an initially slow response.

Most schools reopened last week except for about 120 mostly in Seoul, Gyeonggi province surrounding the capital and Busan, the second-largest city.

There is no known vaccine for MERS, which has a mortality rate of 35 percent, according to the WHO.

The outbreak sparked alarm elsewhere in Asia, with Thailand confirming its first MERS patient on Thursday.

An Omani man, 75, who was recovering from the virus in Bangkok was "slightly better" on Saturday, a health ministry spokesman told AFP.

On Sunday, Thailand's Public Health Minister Rajata Rajatanavin told Reuters that no other cases in Thailand had been confirmed.