BUJUMBURA - Heavy gunfire and grenade explosions that have rocked, since Thursday night, several neighborhoods in the Burundian capital Bujumbura, have prevented people from going to work on Friday.

Police sources said that it was an attack against Musaga in the south and Ngagara in the north of the capital Bujumbura.

"Criminals attacked Musaga and Ngagara, but police agents are pursuing them. We have urged citizens in some neighborhoods that are unsafe to remain in their homes for security reasons," said Burundian Police Spokesman Pierre Nkurikiye.

Witnesses told Xinhua that heavy gunfire and explosive devices were blasted around 03:30 local time early on Friday in several neighborhoods including Ngagara, Musaga, Nyakabiga and Kanyosha.

They said that gunfire and explosions were also heard inside some military barracks including Ngagara and the Military Academy (ISCAM).

Activities are at a standstill in Bujumbura city center on Friday.

In a tweet message, Willy Nyamitwe, senior communication at the Burundian president's office said, "When international observers are around, we often get night gunfire. Tonight (Thursday night), gunmen tried to attack military camps, but they failed."

Burundian Army Spokesman Colonel Gaspard Baratuza, in another tweet message said, "Gunfire was heard near Mpimba prison with the intention to free inmates, but in vain."

Burundi is facing a political turmoil since April when President Pierre Nkurunziza announced his bid for a third term in violation with the constitution, according to the opposition and the civil society.

This crisis led to the killing of more than 300 persons and forced some 200,000 persons into exile in neighboring countries.