South Korea on Thursday confirmed that a man who died a day earlier had been infected with Middle East Respiratory Syndrome (MERS), the third fatality in a virus outbreak that has fueled growing alarm in the country.
The 82-year old South Korean, in hospital with asthma and bacterial pneumonia, had shared a room with others infected with MERS and died on Wednesday night, the health ministry said in a statement.
The victim became the 36th confirmed MERS infection in South Korea, which has the most cases outside the Middle East.
More than 1,100 schools were closed in South Korea on Thursday, while North Korea called for border checks.
South Korean President Park Geun-hye has demanded that everything be done to halt the outbreak, which began two weeks ago, brought into the country by a South Korean man returning from a business trip to the Middle East.
MERS first appeared in 2012 in the Middle East, where most of the 442 fatalities have been.
About 1,600 people have been quarantined in South Korea, most of them at home but some in medical institutions, a health ministry official said.
Soldiers have been confined to base in areas near hospitals where outbreaks have occurred, while parents from those areas may not visit children in the armed forces, a defense ministry official said.
Among the five other new South Korean cases reported on Thursday were two health workers who treated infected patients.
"We are in a war," said an official earlier on Thursday at a health center in Seoul's wealthy Gangnam district, where panic spread when medical workers in protection suits were spotted near a hotel.
The official said a Middle Eastern guest at the hotel fell ill and was later quarantined in hospital.
MERS is caused by a coronavirus from the same family as that which caused SARS, or Severe Acute Respiratory Syndrome (SARS), which emerged in 2002-2003 and killed around 800 people worldwide.
MERS has a much higher death rate, of 38 percent, according to the World Health Organisation, but also spreads far less swiftly than SARS from person to person, making it less of a threat for now.
North Korea had asked the South to provide heat-detecting cameras to monitor temperatures of South Korean workers traveling to the inter-Korean Kaesong Industrial Complex, just north of the border, a South Korean government official said.
South Korea lent North Korea three cameras to use at the complex during the recent scare over Ebola, the official said.
The WHO has not recommended travel curbs, but about 7,000 people from mainland China, Hong Kong and Taiwan had canceled trips to South Korea as of June 2, a spokesman for the Korea Tourism Organisation said.
Japan said it was looking into possible quarantine measures for people arriving from South Korea.
China last week reported its first case, that of a South Korean man who tested positive after breaking a voluntary house quarantine and traveling to Hong Kong and on to mainland China.
Authorities have been criticized for being slow to respond to the initial spread of MERS.
It took several days for the 68-year-old man returning from the Middle East to be diagnosed, during which time he infected people at health facilities where he had sought treatment.
All of South Korea's cases have been traced to the man who visited Saudi Arabia and the United Arab Emirates, the countries with the most MERS cases.
The man whose death was confirmed on Thursday was the sixth person in the South Korean outbreak to get the virus through tertiary infection, meaning he caught it from a patient infected by the original carrier. All the other cases have been traced directly to the "index" patient.
As many as 1,164 schools in South Korea had closed or canceled classes by Thursday, the Ministry of Education said.
While there has been no sustained human-to-human transmission, the virus could change and spread rapidly.
South Korea's new cases bring the total number globally to about 1,180, based on World Health Organization (WHO) data, with at least 442 related deaths.