In a nationwide TV address, Pierre Nkurunziza warned that any more attempts to seize power by force would "bring war, poverty and other atrocities we have seen in this country."
The attempted coup -- announced Wednesday over the radio by an army general while the President was out of the country -- was launched in the wake of deadly protests over his controversial intention to extend his rule beyond term limits. The unrest sparked fears that Burundi could plunge into ethnic violence, with the country's history of civil war making it vulnerable to deep divisions.
Shortly after the President returned from his Tanzania summit Friday, authorities said that they had arrested Army Gen. Godefroid Niyombare, as well as the others involved in the failed plot. They will be charged with mutiny in a military court, said Willy Nyamitwe, a government spokesman.
Nkurunziza sent a tweet Friday congratulating security forces on "their patriotism" and Burundians "for their patience."
Coup called a 'joke'
Shortly after Niyombare announced the attempted coup, the government downplayed it.
Reports of a coup are "a joke," the government spokesman said. The President's office said some soldiers had declared an "imaginary" coup and appealed for calm, saying security forces are looking for the culprits.
Nkurunziza urged citizens not to panic.
"We ask all the people of Burundi to stay calm in the face of the impostor," the President tweeted Thursday. "The situation is under control and the constitutional order has been safeguarded."
The international airport in the capital of Bujumbura was shut down; so were the nation's land borders. Fear and uncertainty reigned, as gunfire and explosions rang out in Bujumbura for hours Wednesday and Thursday.
"People are staying indoors, not moving," said Gad Ngajimana, who lives in Bujumbura. "The faces of the people -- they are very scared. Either it is a coup or not, no one knows."
Niyombare, a former head of Burundian intelligence, was fired by the President in February.
Protests against the President
Animosity against the President started last month when he expressed his intention to extend his 10-year rule.
Nkurunziza is seeking a third term, which is prohibited by the agreement that ended the 1993-2003 civil war. Protesters determined to prevent his candidacy have demonstrated in the capital, and police have met them with deadly force.
Tensions between anti-Nkurunziza protesters and police continued Friday. In the Musaga area of the capital, police fired their guns into the air in an attempt to move protesters who had set up barricades in the area. No one was injured, and the protesters appeared to disperse.
Many shops were closed, but vendors were selling goods on the streets, and pedestrian traffic appeared to be close to normal.
Nkurunziza officially registered last week to run for a third term, further angering protesters. The attempted coup punctuated weeks of protests.
Burundi's constitutional court ruled he is eligible to run again because he was picked by Parliament, not elected by the people, during his first term.
At least seven candidates have registered for the presidential race scheduled for next month. Among them is prominent opposition leader Agathon Rwasa, who helped lead rebel fighters in the country's civil war.
East African Community leaders called for the elections to be postponed, saying conditions are "not conducive" to holding them.
Refugees stream into neighboring nations
As protesters clashed with security forces over Nkurunziza's decision to run for office, about 105,000 refugees have fled to the Democratic Republic of Congo, Tanzania and Rwanda, according to the United Nations.
While the current crisis is rooted in politics, some observers fear the government might try to stoke ethnic animosities in a last-ditch effort to retain power.
Burundi, like its neighbor Rwanda, has a Hutu majority and a Tutsi minority
The last time the nation plunged into ethnic violence fueled by tensions between ethnic Hutus and Tutsis, the resulting civil war left 300,000 people dead.
The tiny nation is home to about 10 million people.