Which of the following is the main cause of the attack?

United Nations and French helicopters in Ivory Coast have attacked forces and installations controlled by Laurent Gbagbo who is refusing to step down after last year’s presidential election. A UN spokesman said the air strikes were aimed at destroying Mr Gbagbo’s heavy weaponry which had earlier been used to assault the UN headquarters in Abidjan. From Abidjan here is Mark Doyle.
    Two United Nations and at least six French helicopter gunships were involved in the attacks. Eyewitnesses said they hit the presidential palace and in a different part of the city, the presidential residence, where the United Nations says Mr Gbagbo is living in an underground bunker. The United Nations has clearly taken sides in this war between a man who won a United Nations certified election and a man who refuses to accept that he lost.