Belarus has violated an international arms embargo by sending three attack helicopters to military forces supporting Ivory Coast's longtime ruler who refuses to cede power, the U.N. chief said, in a dramatic escalation of the nation's political conflict.

Belarus denied the allegations, which come after a week of intensified street battles in Abidjan and the country's west that left several dozen dead.

The clashes between the army controlled by Gbagbo and a new armed group fighting on behalf of his political rival prompted the United Nations to warn that the country was on the brink of re-igniting civil war.

The U.N. refugee agency said on Monday that as many as 30,000 civilians had fled the Abobo neighborhood of Abidjan where the fighting raged over the weekend. They could be seen streaming out of the affected area carrying suitcases on their heads.

The office of the United Nations Secretary-General Ban Ki-moon said that the first delivery of helicopters from Belarus reportedly arrived Sunday, and additional flights were scheduled for Monday.

"This is a serious violation of the embargo against Cote d'Ivoire, which has been in place since 2004," Ban's statement said, using the country's French name. "The violation has been immediately brought to the attention of the Security Council's committee charged with the responsibility for sanctions."

Belarusian Foreign Ministry spokesman Andrei Savinykh rejected the accusations on Monday, calling them "groundless."

"Belarus hasn't supplied any weapons to Ivory Coast in violation of U.N. sanctions," Savinykh told The Associated Press, adding that the country has strictly observed all decisions by the U.N. Security Council and has efficient controls over arms trade.

The Belarusian authoritarian leader Alexander Lukashenko is often called Europe's last dictator and has led the ex-Soviet state since 1994. He was declared the winner of an election widely regarded as fraudulent that took place just weeks after the Ivory Coast vote.

Gbagbo's air force was destroyed by the French military during the country's earlier civil war, which erupted in 2002. The arrival of the attack helicopters means that the Gbagbo regime now has air power, which could not only endanger civilian areas but also the Golf Hotel where the man considered to be the legitimate president of Ivory Coast is holed up with hundreds of his supporters.

Alassane Ouattara was declared the winner of the Nov. 28 presidential election by the country's electoral commission. Gbagbo refused to accept defeat even though the U.N. reviewed the results from over 20,000 polling stations before certifying Ouattara's victory. Ouattara was forced to take refuge inside the hotel, where he is now under 24-hour U.N. guard.

Several hundred U.N. peacekeepers are stationed on the grounds, but it is not clear if the U.N. is set up to protect the hotel from an air assault.

The hotel houses Ouattara's government, including his Cabinet, as well as his newly launched TV station which is attempting to act as a counterweight to the pro-Gbagbo propaganda disseminated on state-owned TV.

Gbagbo already has demanded that the U.N. leave the country. He accuses them of bias and last week, a militant youth leader allied with Gbagbo called on supporters to stop and search all U.N. vehicles. Three peacekeepers were wounded over the weekend and four of their cars were sabotaged, U.N. spokesman Hamadoun Toure said.

Multiple delegations of African leaders have come through Abidjan in an attempt to persuade Gbagbo to leave peacefully. He has rejected all their proposals, including offers of amnesty and a comfortable exile abroad.

A regional body of 15 countries in West Africa has said it will consider a military assault as a final resort if Gbagbo does not step down.

He is being strangled financially because the European Union has prohibited European ships from docking in its port. The regional central bank headquartered in the neighboring country of Senegal also has frozen Gbagbo's access to state accounts and it is unclear if he will be able to pay civil servant employees in February.


Associated Press writers Yuras Karmanau in Minsk, Belarus; and Peter James Spielmann in New York contributed to this report.