Media playback is unsupported on your device Media caption Incumbent Laurent Gbagbo's "young patriots" cross the river in boats and head towards Abidjan's city centre

France has sent extra troops to Ivory Coast's main city, Abidjan, and taken control of its airport.

A French military spokesman told the BBC there was a security vacuum as forces formerly loyal to incumbent Laurent Gbagbo changed sides.

Fighting continues between Mr Gbagbo's troops and supporters of his rival, UN-recognised President Alassane Ouattara.

The city's pro-Gbagbo TV station called for people to mobilise against the French '"occupation".

Mr Ouattara's forces are reported to be planning a further advance towards the presidential palace and have imposed a curfew on the city.

UN spokesman Hamadoun Toure told the BBC he had heard gunfire near the palace, adding that the situation was very tense.

Analysis A spokesman for the Ouattara government said Laurent Gbagbo now only controlled the presidential palace and the presidential residence. But Abidjan's residents report a more mixed picture with armed groups loyal to the two sides roaming the city. There are formal forces but also the youth militia groups that have been armed as well. So far, pro-Ouattara forces have been unable to capture any of the key targets they have been fighting for since Thursday - the presidential offices, residence, state television and major barracks. Several key military leaders, including the head of the army have abandoned Mr Gbagbo, but his forces do still have superior weaponry including several tanks. There are several sections of the city that are without electricity, and the way the system works means that the electrical pumps are not working either so the water is off as well. It is very difficult for people to get out of their homes to buy basic supplies, even a bottle of water, just because of the violence going on in the streets.

France has sent an extra 300 soldiers to Ivory Coast, defence ministry spokesman Thierry Burkhard said, taking the total French force to about 1,400.

The airport had been secured by UN troops since Friday, but the French move meant the airport was now able to re-open, Mr Burkhard told the BBC.

The aim of the reinforcement was "to take control over the airport which was also done in co-ordination with the UN mission, to allow the re-opening of this airport to civilian airlines and military flights", he said.

Mr Burkhard added that the force's mission remained primarily the protection of French nationals, who were being threatened by looters.

"We are currently experiencing in Abidjan a security vacuum because the Ivorian security forces, which until now followed the orders of Mr Gbagbo, answered in great numbers the rallying call made by President Ouattara," he said.

There were no immediate plans to start evacuating foreigners, he said, though about 1,600 were sheltering in a French army camp.

They include about 700 French nationals, some 600 Lebanese citizens and 60 Europeans of assorted nationalities, French media report.

'Lives at stake'

Ivorian state TV, which is controlled by Mr Gbagbo, accused the French troops of preparing a genocide like the one in Rwanda in 1994, when more than 800,000 people were killed.

A strap line on state TV on Sunday read: "[French President Nicolas] Sarkozy's men are preparing a Rwandan genocide in Ivory Coast."

Mr Sarkozy has called a cabinet meeting for Sunday afternoon to discuss the crisis in Ivory Coast.

Ivory Coast: Battle for power World's largest cocoa producer

Once haven of peace and prosperity in West Africa

Alassane Ouattara recognised as president-elect in 2010

International sanctions imposed to force Laurent Gbagbo to go

Hundreds killed, one million have fled since disputed election

9,000 UN peacekeepers monitor 2003 ceasefire In pictures: Battle for Abidjan Q&A: Ivory Coast crisis Profile: Laurent Gbagbo Profile: Alassane Ouattara

On Saturday, heavy artillery fire was heard in Abidjan as the two sides fought for key sites including the presidential palace, the headquarters of state TV and the Agban military base.

Four UN soldiers were seriously wounded when special forces supporting Mr Gbagbo fired a rocket-propelled grenade at a UN armoured vehicle.

The west of Ivory Coast has also seen vicious battles between rival militias and ethnic groups. On Saturday, the Caritas aid agency said its staff had found the bodies of hundreds of people in Duekoue, and estimated that 1,000 may have died.

The killings occurred between 27 March and 29 March in the Carrefour district, which was controlled at the time by fighters loyal to Mr Ouattara, spokesman Patrick Nicholson told the Associated Press news agency.

"Caritas does not know who was responsible for the killing, but says a proper investigation must take place to establish the truth," he said.

Most of the 1,000 peacekeepers based in Duekoue had been protecting about 15,000 refugees at a Catholic mission there, Mr Nicholson added.

The International Committee of the Red Cross put the death toll at about 800, while the UN said more than 330 people were killed as Mr Ouattara's forces took over Duekoue, most of them at the hands of his fighters. However, more than 100 of them were killed by Mr Gbagbo's troops, it added.

Sidiki Konate, a spokesman for Mr Ouattara's government, said that while some people had been killed in the fighting between the two sides in recent days, there had been no deliberate killings of Gbagbo supporters.

ICRC staff who visited Duekoue on Thursday and Friday to gather evidence said the scale and brutality of the killings were shocking.

Tens of thousands of women, men and children have fled the fighting.