Armed men attacked a gendarmerie barracks in the main Ivory Coast city of Abidjan overnight, while a separate armed group attacked an army post to the north, military and UN sources said.

Gunmen opened fire on the paramilitary police barracks in the Yopougon district in the west of the city at around 3:00 am (0300 GMT) but the attackers were repelled, a source at the army chief of staff told AFP.

A UN source said a prisoner in custody had also been killed in the fighting, while another military source said one gendarme had been wounded and several vehicles burned.

"There was heavy fighting for two hours," said a resident of the district, who was backed up by other local people and a Western security source, who said the attackers used assault rifles and rocket-launchers.

"A prisoner who was in detention was killed, the building was entirely sacked and seven vehicles were burned out," Sylvie Van Den Wildenberg, spokewoman for the UN Operation in Ivory Coast (ONUCI) told AFP.

Overnight meanwhile, gunmen attacked an army checkpoint at Agbaou, a village about 100 kilometres (60 miles) north of the economic capital, Van Den Wildenberg said.

"The provisional toll is two (army) soldiers wounded," she added. The attack took place around 2:45 am.

President Alassane Ouattara's regime has since August been confronted with a series of often deadly raids targetting the security forces and strategic sites.

The government blames them on supporters of former president Laurent Gbagbo, who was toppled in April 2011 after a bloody post-electoral power struggle.

The last attack took place last weekend after a lull of several weeks, when two members of the Ivory Coast Republican Forces (army) were killed in Agboville, north of Abidjan.

ONUCI chief Bert Koenders condemned the attacks "with the very greatest firmness".

The overnight raids came after a court on Thursday freed on bail eight people close to Gbagbo. They included his former prime minister Gilbert Ake N'Gbo, who was detained during the power struggle of December 2010 to April 2011, when Gbagbo refused to admit defeat at the polls to Ouattara.

The five months of clashes claimed some 3,000 lives.

The move by the court, seen as a bid to ease tensions that have built up in recent months, was welcomed by Gbagbo's Ivorian Popular Front (FPI) party.

"This is already an important step which needs to be encouraged so that the others follow," FPI president Sylvain Miaka Oureto told AFP.

Several leading figures of the former regime, including ex-First Lady Simone Gbagbo, are still behind bars. Dozens of civilians and soldiers who served in less senior posts are also in jail, often in the north of the country.

In November 2011, Gbagbo himself was transferred to the International Criminal Court in The Hague, where he is accused of crimes against humanity.

The eight people freed Thursday have been accused in some cases of genocide and "blood crimes", in others of threatening state security or economic misdemeanours.

Bail was also granted Thursday to Franco-Ivorian businessman Ibrahim Magassa, according to a court source. He was detained in connection with a trade dispute.