Gun shots were fired overnight in Guinea-Bissaus capital Bissau and continued into Friday morning, Reuters reporters said.

The circumstances of the shooting remain unclear.

One reporter said gunshots were first heard after midnight in the neighbourhood of Antula, on the outskirts of the capital, where an army general lives.

Military vehicles were on the streets on Friday morning as residents commuted to work and school.

Gunshots could still be heard but were less frequent than during the night.

Another reporter heard gunshots not far from the presidential palace.

There have been at least 10 coups or attempted coups in Guinea Bissau since independence from Portugal in 1974.

Only one democratically elected president has completed a full term in the West African nation south of Senegal.

At least six people were killed during a failed attempt to overthrow President Umaro Sissoco Embalo in February last year.

At the time, Embalo suggested it was linked to the governments fight against drug trafficking rather than an army plan to seize power.

West Africa has been hit by a string of military takeovers over the past three years, including two in Mali, one in Guinea, two in Burkina Faso and one in Gabon.

Sierra Leones government pushed back a military attempt to overthrow it over the weekend.

More than 20 people were killed as gunmen in the capital Freetown attacked military barracks, a prison and other locations on Sunday, freeing about 2,200 inmates. (Reuters/NAN, excluding headline)