South Korea has reported its fifth death from MERS as the government vowed "all-out" measures to curb the largest outbreak outside Saudi Arabia, including tracking mobile phones of those in quarantine.

The number of infections rose to 64 after 14 new cases, including one death, of Middle East Respiratory Syndrome (MERS) were confirmed on Saturday night, the health ministry said.

All of the 14 were among a group of 1820 quarantined until Saturday after being exposed to those diagnosed earlier, the ministry added.

However, Busan city authorities reported an additional case in the country's southern port and second-largest city, sparking alarm that the outbreak may spread nationwide.

The case was not included among the 14 new infections confirmed by the health ministry.
Acting Prime Minister Choi Kyung-Hwan vowed on Sunday that "all-out efforts" would be made to curb the spread of the disease in Asia's fourth-largest economy.

He urged the public not to panic, saying all 64 patients had already been in hospital.

"We can put the situation under control because... the outbreak is not spreading to the outside community," Choi said in a press conference.

"People should not overreact and should cooperate closely (with the government) to minimise negative impact on the economy," he said.

The government will step up monitoring on those placed under observation, including tracking the locations of those in quarantine at home via their mobile phones, Choi said.

"Please understand that it is an inevitable measure to ensure the safety of your neighbours and families," Choi said.

Most of those under quarantine have been told to stay home and strictly limit their interactions with others, while some have been isolated in state hospitals.

The first case - reported on May 20 - was of a 68-year-old man diagnosed in the city of Pyeongtaek, about 65 kilometres south of Seoul, after a trip to Saudi Arabia.

With the number of new cases growing on a daily basis and public fear rising, more than 1300 schools were closed temporarily and school trips, public events and sports games were cancelled across the country.

More than 20,000 foreign travellers have cancelled planned tours to the South from Monday to Thursday, Seoul's tourism board said.

The World Health Organisation (WHO) said on Friday it would send a team of experts to South Korea for a joint mission with Seoul in collecting information of the outbreak.

MERS has now infected more than 1110 people globally, with 437 deaths. More than 20 countries have been affected, with most cases in Saudi Arabia.

The virus is considered a deadlier but less infectious cousin of Severe Acute Respiratory Syndrome (SARS) which killed hundreds of people when it appeared in Asia in 2003.