The UN secretary general has urged Ivory Coast's internationally-backed president to investigate hundreds of deaths blamed partly on his supporters. Ban Ki-moon said he was "concerned and alarmed" about the reports, from the town of Duekoue, but Alassane Ouattara said his followers were not involved. The BBC's Andrew Harding, in Duekoue, says UN workers have found hundreds of bodies. In the main city of Abidjan, fighting has continued between rival troops. Mr Ouattara's forces have beaten back supporters of his rival, incumbent Laurent Gbagbo, to a few key locations. UN spokesman Hamadoun Toure told the BBC he had heard gunfire near the presidential palace, currently held by Mr Gbagbo, adding that the situation was very tense. The airport, which had been secured by UN troops since Friday, is now under the control of French troops, allowing it to re-open. There were reports that the UN was evacuating around 200 employees from Abidjan. But the city's pro-Gbagbo TV station called for people to mobilise against what it called a 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. 'Shocking brutality' The violence in Duekoue happened last week, when Mr Outtara's fighters moved south ousting Mr Gbagbo's troops from large swathes of the country. Both sides have said the other was responsible. The UN said on Saturday that more than 330 people had been 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. "The secretary general expressed particular concern and alarm about reports that pro-Ouattara forces may have killed many civilians in the town of Duekoue in the west of the country," UN spokesman Martin Nesirky said. "The secretary general said those responsible should be held accountable." UN officials are still investigating and say the final death toll may be higher. Caritas aid agency estimated that 1,000 may have died. Mr Ouattara said his supporters were not involved, but told Mr Ban he had ordered an investigation into the killings and would welcome an international inquiry, Mr Nesirky said. Looting threat 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 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 told the BBC. 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. Source: BBC