Employees from Korean Air disinfect the interior of its airplane in Incheon, South Korea, June 5, 2015. [Photo/Agencies]

SEOUL - South Korea reported a jump in cases of Middle East Respiratory Syndrome (MERS) on Monday and local officials ordered the closure of nearly 2,000 schools nationwide, while an 80-year-old man became the sixth fatality from the outbreak.

Singapore postponed or cancelled all school trips to the country, although the head of the World Health Organization (WHO) said she believed South Korea would be able to control the further spread of the virus by taking appropriate measures.

The latest MERS patient to die in South Korea had been hospitalised for pneumonia when he was infected, officials in the city of Daejeon said on Monday.

The Health Ministry announced 23 new infections, bringing the total to 87. South Korea now has the second highest number of infections in the world after Saudi Arabia, according to data from the European Centre for Disease Prevention and Control.

Underlining concern about the spread of the disease, South Korean authorities said they would track the cellphones of more than 2,300 people under quarantine who may have been in contact with patients. Some of those under quarantine are in healthcare facilities although most are at home.

A team of experts from the WHO was due to begin work on Tuesday to evaluate the response to the outbreak, including why it had spread so fast and advise on further measures.

The South Korean culture of families looking after their loved ones at hospitals may have been part of the reason for it to spread within healthcare facilities, WHO Director-General Margaret Chan told Yonhap news agency.

All known South Korean infections have taken place within healthcare facilities, where it is common for family and friends to make lengthy visits, sometimes around the clock.

The WHO has not advised any travel restrictions.