Washington: UN Secretary General Ban Ki-moon and US President Barack Obama have expressed concern about rising violence in the Ivory Coast.

"They expressed their concern about the violence there and the need to enable the legitimately elected president to be able to govern," US ambassador to the United Nations Susan Rice told reporters at the White House.

Obama and Ban met at the White House on Monday as UN sources said forces loyal to strongman Laurent Gbagbo opened fire on UN sanctions experts who tried to check on a suspected breach of an international arms embargo of the country.

Ban later toured the Holocaust Memorial Museum in Washington, where he told reporters that Gbagbo should step down and hand power to his rival Alassane Ouattara in a presidential election held in November.

The international community has widely recognized Ouattara as the winner of the election, but Gbagbo, who has been in power for 10 years and survived a bid to oust him in 2002, has refused to accept the result and stand aside.

"The winner of the election in Cote d'Ivoire is Mr Ouattara, and Mr Gbagbo should cede power to preserve peace and stability and the future of Cote d'Ivoire," Ban said after touring the museum, which was set up as a memorial to the six million victims of the Holocaust in  World War II.

There have been increasing clashes between supporters of Gbagbo and Ouattara in recent days.    
UN sources said that on Monday forces loyal to Gbagbo opened fire on UN experts who had gone to Yamoussoukro airport to investigate reports that the former Soviet republic of  Belarus had sent attack helicopters to Ivory Coast.