The World Health Organization (WHO) said on Wednesday South Korea's outbreak of Middle East Respiratory Syndrome (Mers) is a 'wake-up call' but does not constitute a global emergency, as the country reported eight new cases.

A total of 162 people have been infected and 20 people have died in South Korea's Mers outbreak, which began last month and is the largest outside Saudi Arabia.

The outbreak has been traced to a 68-year-old South Korean man who returned from a business trip to the Middle East in early May, and the WHO said it expected new cases in coming weeks, although the numbers appear to be declining.

Members of the WHO's emergency committee agreed unanimously that the outbreak did not qualify as a public health emergency of international concern - a rating that would have triggered a coordinated, worldwide response.

"This outbreak is a wake-up call," the Geneva-based agency said. "In a highly mobile world, all countries should always be prepared for the unanticipated possibility of outbreaks of this, and other serious infectious diseases."

It added, however, that there was no current evidence of the disease spreading easily within communities, and there was no need for any international travel or trade restrictions.

The eight new South Korean cases marked a rise from the four and five the previous two days, but below double-digit daily increases reported last week.

"It is absolutely critical to keep high-level surveillance, keep up high levels of monitoring," the WHO's assistant director general, Keiji Fukuda, told a briefing in Geneva.

More than 6,500 people are in quarantine in South Korea, either at home or in health facilities.

South Korea had come under criticism for its early response to the Mers outbreak.

"They are really pulling out all the stops now and trying to shut this down. It's very impressive," Fukuda, who led a WHO team of experts who visited South Korea last week, told Reuters.

South Korea said 19 people diagnosed with the Mers virus had recovered and been discharged from hospital.

The latest Mers patient to die in South Korea was a 54-year-old woman who had bronchiectasis and high blood pressure. Nearly all of the fatalities were people who had existing ailments or were elderly.

All of the infections known to have occurred in South Korea have taken place in healthcare facilities. Three hospitals have been at least partially shut and two have been locked down with patients and medical staff inside.

Mers is caused by a coronavirus from the same family as the one that triggered China's deadly 2003 outbreak of Severe Acute Respiratory Syndrome (SARS).

The vast majority of Mers infections and deaths have been in Saudi Arabia, where more than 1,000 people have been infected since 2012, and about 454 have died.-Reuters