( CNN ) -- The United Nations on Monday accused Belarus of defying an arms embargo against Ivory Coast by delivering three attack helicopters to the disputed president of the West African nation . A spokesman for U.N. Secretary-General Ban Ki-moon said that the helicopters and other related materiel `` are reportedly being delivered at Yamoussoukro , '' the nation 's capital , for Laurent Gbagbo 's forces . Ban is pushing for an urgent meeting of the U.N. Security Council on the matter , the spokesman said . `` The first delivery arrived reportedly on a flight which landed this ( Sunday ) evening and additional flights are scheduled for Monday , '' the spokesman said in a statement . U.N. spokesman Martin Nesirky said Monday afternoon that U.N. officials on the ground in Ivory Coast were unable to confirm whether the delivery was made , saying they were forced to withdraw from the airport before they were able to verify the report . U.N. officials later said that the team sent to investigate the possible breach of sanctions was fired upon Monday by local security forces in the Ivory Coast . Gbagbo , the nation 's incumbent leader , is clinging to the presidency despite an international call for him to step down after an electoral commission declared challenger Alassane Ouattara the winner of a November election . The deliveries violate an arms embargo that has been in place since 2004 , Ban 's spokesman said . Andrei Savinykh , a spokesman for the Belarusian Foreign Ministry , vehemently denied the allegation , calling it part of a campaign of `` lies and slander '' against Belarus . A `` destructive information attack is being carried out '' against Belarus , said Savinykh , according to the Belarus state-run Belta news agency . Violence in Ivory Coast escalated sharply over the past week , after four African heads of state left Abidjan . They had been given a mandate by the African Union to find a `` binding solution '' to the post-election crisis in Ivory Coast . Gbagbo and Ouattara supporters have clashed in the central cities , Yamoussoukro and Daoukro , in addition to ongoing fighting in Abidjan . Ouattara is holed up in the Golf hotel in Abidjan under the protection of U.N. peacekeepers . CNN 's Maxim Tkachenko and Joe Vaccarello contributed to this report .
NEW : A U.N. team sent to investigate the possible breach of sanctions is fired upon . A spokesman for the government of Belarus denies breaking the embargo . The secretary-general is pushing for an urgent meeting of the U.N. Security Council . A spokesman for Ban Ki-moon says the first helicopter reportedly arrived Sunday .