Burundi: Gunfire, uncertainty as government downplays coup attempt

(CNN)Gunfire erupted in Burundi on Thursday, hours after an army general announced a coup and the President's spokesman dismissed it as a "joke."

Political infighting sparked fears that Burundi would plunge into ethnic violence -- with the central African nation's history of civil war making it especially vulnerable to deep divisions.

Sporadic gunshots rocked Bujumbura, the capital, following an attempt to overthrow President Pierre Nkurunziza on Wednesday.

But the President downplayed any coup attempt, urging citizens not to panic.

"We ask all the people of Burundi to stay calm in the face of the impostor," Nkurunziza tweeted. "The situation is under control and the constitutional order has been safeguarded."

Later Thursday, Nkurunziza posted a Twitter message declaring he has returned to his country. He also did "congratulate the army and the police for their patriotism," before congratulating "Burundians for their patience."U.S. diplomats were "deeply concerned," said Jeff Rathke, State Department acting deputy spokesman.

"Our embassy has received reports that the airport continues to be closed and that the land borders may also be closed or restricted at this time," Rathke said.

He told reporters that "President Nkurunziza remains the President of Burundi," but urged Americans there to "exercise extreme caution." He also said that "travel in Bujumbura currently is not safe."

The United Nations Security Council has condemned the violence in Burundi and "called for the swift return of the rule of law," the French mission at the U.N. said r