ABIDJAN, Ivory Coast – The United Nations warned Thursday that violence is spreading across Ivory Coast, citing nearly two dozen rapes in the country's west and one case where a political opponent was sexually tortured.

Local U.N. human rights chief Simon Munzu said Thursday that 23 women have been raped in the last week in western Ivory Coast, where 16,000 people have taken refuge since the disputed Nov. 28 presidential runoff vote. Another 29,000 people have fled across the border to Liberia.

"We regret that as a result of the ethnic crashes that we witnessed in Duekue in particular recently, a number of rape cases have come to our attention," Munzu said.

In the almost two months since the presidential election, incumbent leader Laurent Gbagbo has refused to cede power even though the international community says his rival Alassane Ouattara won the vote.

African nations have also voiced support for Ouattara. On Thursday, Ouattara received an invitation to pay a state visit from President Seretse Ian Khama of Botswana.

Khama said the invitation to visit the southern African nation was "in recognition of (Ouattara's) victory of the presidential elections."

Munzu said Thursday that security forces loyal to Gbagbo had used sexual torture techniques on at least one Ouattara supporter, following a raid on Ouattara's party headquarters two weeks ago in which 63 people were arrested.

"This young man was sodomized by eight members of the Republican Guard who wanted to extract information about his fellow members of the (pro-Ouattara) RHDP," Munzu said.

There was no immediate reaction from Gbagbo's camp, though his spokesman has previously denied allegations that security forces were behind cases of abduction and torture.

The U.N. voted Wednesday to beef up its peacekeeping force in the country by sending 2,000 more troops, bringing the total to almost 13,000 in this volatile West African country.

Gbagbo's government reacted harshly to the announcement Thursday, reiterating its claim that the U.N. has overstepped its mandate and is no longer impartial.