Gunfire has erupted around the presidential palace in the West African state of Guinea-Bissau, after the army chief of staff died in a bomb attack.
Renegade soldiers have shot dead the president of Guinea-Bissau, Joao Bernardo Vieira, reports say.
It is not clear if a coup attempt is under way, amid reports that President Joao Bernardo Vieira has been killed.
Officials and residents gave news of the death just hours after that of the army chief of staff, Mr Vieira's rival.
The AFP news agency quotes an army spokesman saying the president had been killed by soldiers as he tried to flee.
Gunfire is said to be resounding around the capital, Bissau, and it is unclear who is in control of the West African nation.
Guinea-Bissau is one of the world's poorest states. It has a history of coups and is a drug trafficking centre.
Bissau is one of the world's poorest states. It has a history of coups and is a drug trafficking centre.
"President Vieira was killed by the army as he tried to flee his house which was being attacked by a group of soldiers close to the head of the chief of staff Tagme Na Waie, early this morning," Zamora Induta told AFP.
He accused Mr Vieira of being responsible for the death of army chief of staff General Batista Tagme Na Wai.
The general died after a blast late on Sunday that destroyed part of the military headquarters.
Renegade soldiers last November attacked the presidential palace with automatic weapons in a failed coup attempt.
Revenge
An aide to General Tagme, Lt Col Bwam Nhamtchio, told AFP the chief of staff was in his office when Sunday's blast went off.
"He was gravely wounded and did not survive his injuries. This is a loss for all of us," Lt Col Nhamtchio said.
State radio has confirmed General Tagme's death.
At least five people were reportedly killed in the explosion.
Following the attack on the military HQ, officers ordered two private radio stations in the city to cease broadcasting.
"For the security of the journalists, you must close the radio station and stop broadcasting. It's for your own safety," armed forces spokesman Samuel Fernandes told reporters at one station.
"We are going to pursue the attackers and avenge ourselves," he added.
Plagued by coups
It is not yet clear who was behind the attack but it once again highlights the country's fragility, the BBC's West Africa correspondent Will Ross says.
After last November's attack, the president was subsequently given his own militia for protection.
In January, that militia was accused of trying to kill the head of the army and was then disbanded.
Guinea-Bissau has been plagued by coups and political unrest since it gained independence from Portugal in 1974.
President Vieira, just like the country's previous leaders, has relied on the army to stay in power, and personal rifts have made it a rocky relationship, our correspondent says.
Guinea-Bissau - a major transit point for Latin American cocaine headed for Europe - has also been destabilised by the effects of drug trafficking.
Some officials in the army are known to have become involved in the trade, our correspondent adds.
