Pyongyang says forces will be sent to Kaesong, an inter-Korean industrial park along the border where a liaison office was blown up by North Korea earlier this week.
The office, north of the Demilitarized Zone, appears to have been empty when it was destroyed. The act follows threats from Pyongyang, and experts say provocations from the North will likely continue.
According to multiple news reports, the banner was taken down after President Trump and senior State Department officials expressed displeasure with it.
The move is the latest sign of deterioration in relations between North and South Korea. On Tuesday, North Korean officials did not answer a routine daily call from the South.
A study of patients who initially tested negative for the virus, but weeks later tested positive again, has found they do not appear to pass the disease to personal contacts such as family members.
Both countries eased some of their intensive rules after new cases slowed to a trickle. But clusters have cropped up again this month, and authorities are ramping up testing to try to curb the spread.
The country had prepared to welcome students back to classrooms on Wednesday, but dozens of new virus cases linked to nightclubs in Seoul have emerged.
The president has rejected the notion that the U.S. should lead a global response to the crisis. The current pandemic has unfolded in a world where no one has offered international leadership.
The Korean Baseball Organization will begin its new season on May 5, initially without fans. The KBO hopes this week's start of preseason games leads to a smooth opening of the regular season.
Gov. Larry Hogan, a Republican, announced his state paid $9 million for coronavirus test kits from a South Korean company. "If there were an easier way, we certainly would have taken it," Hogan said.