South Korea's health ministry confirmed on Tuesday (Jun 2) that two people have died from Middle East Respiratory Syndrome (MERS), the country's first fatalities from the virus.
A 58-year-old woman, who had been treated as a suspected case of MERS, died of acute respiratory failure on Monday and tests later came back positive for the virus.
The other victim was a 71-year-old man who was confirmed to have the virus several days ago. He died on Tuesday, the health ministry said in a statement.
Six more people were diagnosed with the disease Monday night, it said, bringing the total number of people infected to 25 including the two victims.
The latest outbreak - the largest outside the Middle East - triggered widespread public alarm in the Asia's fourth-largest economy.
South Korea's first case was reported on May 20 and the health ministry said on Monday that a total of 682 people who were exposed directly or indirectly to the virus have now been quarantined or put under special observation.
But more are expected to be quarantined or put under observation as more new cases are confirmed.
Acting prime minister Choi Kyung-hwan vowed "all-out Tuesday efforts" to curb the spread of the virus and ease "growing panic" among South Koreans.
"People believe that the health authorities' response has been inefficient and poor," he said in an emergency meeting with top health officials. "We should use all our national resources to alleviate their concerns," he said.
Middle East Respiratory Syndrome 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.
More than 20 countries have been affected by the virus, which has no known cure or vaccine, with most cases in Saudi Arabia where it has claimed more than 400 lives since 2012.
South Korean President Park Geun-hye has scolded health officials over their "insufficient" response to the outbreak. Health officials were particularly criticised for allowing an infected man to travel to China last week despite warnings from doctors.
The 44-year-old left on a business trip on Tuesday, a day after his father was diagnosed with the virus, and was confirmed on Friday to have been infected himself. The man flew to Hong Kong before travelling on to the Chinese city of Huizhou, where he is being treated under quarantine.
The current outbreak has been traced to a 68-year-old man diagnosed after returning from a trip to Saudi Arabia.