A Joint Chiefs of Staff (JCS) officer in Seoul tested positive for the new coronavirus Tuesday, officials said.

It marks the third COVID-19 case reported among people working at the JCS headquarters in Yongsan, central Seoul, after a civilian employee and another military officer were confirmed to have contracted the virus last month.

Tracing is under way on people who had direct contact with the newly infected officer.

The case came as South Korea and the United States are preparing to stage an annual springtime combined exercise this month.

The defense ministry has said the two countries will decide the details of the computer-simulated command post training in consideration of the virus situation.

Earlier in the day, the defense ministry also said an Army officer and three enlistees in Sejong, some 120 kilometers south of Seoul, have tested positive for the new virus after an infection was reported at their base.

Among some 700 people tested following the initial case, all others except for the four tested negative, it said.

The latest cases brought the total number of infections reported among the military population to 580.

The defense ministry said it will maintain the current social distancing rules for the military, which allow service members to vacation in a limited manner, for another two weeks, while banning one-day off-base trips.

In mid-February, the ministry lifted a vacation ban for enlisted service members that has been in place for over two months, as it lowered the antivirus level by one notch to the third-highest Level 2 in its five-tier alert system.

"We've decided to extend the current Level 2 social distancing until March 14 in line with the government's guidance," a ministry official said.

Under the Level 2 scheme, troops are allowed to go on vacations while strictly adhering to antivirus measures, such as a mandatory quarantine and coronavirus tests. Up to 20 percent of members of each base can take leave at the same time, according to the ministry.

But staying out overnight and meeting outside visitors are banned in principle, it added.

Currently, the government enforces Level 2 distancing for the capital area, home to around half of the nation's 52 million population, and Level 1.5 for other parts of the country.

Restaurants and bars in the capital area are allowed to remain open for an hour longer than before until 10 p.m., and bans on gatherings of five or more people are in place nationwide. The measures are to be in place until March 14.

Nationwide, South Korea reported 344 more COVID-19 cases, including 319 local infections, on Tuesday, raising the total caseload to 90,372, the Korea Disease Control and Prevention Agency (KDCA) said. (Yonhap)