Anger has been building across the country as Haiti's post-quake reconstruction stalls [Reuters]

Demonstrators have blocked the entrance to the UN military headquarters in Port-au-Prince, Haiti, spraying anti-UN slogans on vehicles trying to enter.

A crowd of roughly 100 protesters carrying banners saying "Down with the occupation" were forced back by UN soldiers, Sebastian Walker, Al Jazeera's correspondent in Port-au-Prince, said on Friday.

"Security personnel traded blows with demonstrators, and troops started firing in the air, with helicopters hovering above."

Demonstrators also burned the flag of Brazil, the nation that has contributed the largest contingent to the international peacekeeping force.

"Haitians feel that the presence of [UN] security personnel doesn't offer much in terms of ordinary Haitians living in camps," Walker said.

Although opposition demonstrators remained quiet for several months following the massive January 12 earthquake, a chorus of opposition to Rene Preval, Haiti's president, and to UN forces has become more vocal in recent weeks.

Mandate extended

The political violence comes on the heels of Thursday's announcement by the UN that its peacekeeping force will remain in Haiti at least another year.

The unanimously approved Security Council resolution extended by one year the presence of nearly 9,000 soldiers and around 4,300 police officers - and called for "credible and legitimate" presidential and legislative elections, which are scheduled for November 28.

Rene Preval, who has served as Haiti's president for 10 of the past 15 years, cannot by law run for re-election, and the country remains in a perilous position nine months after a devestating earthquake killed around 300,000 people and left millions more homeless.

An investigation by the Associated Press news agency has determined that none of the $1.15bn in rebuilding funding promised by the US has arrived. There have also been reports of a rise in drug trafficking and criminal-gang activities.

The UN resolution passed on Thursday expressed concern with "the rise in the number of weapons in circulation" and condemned "grave violations against children affected by armed violence, as well as widespread rape and other sexual abuse of women and girls".

The post-election transition to a new government will not happen until next year, and the UN peacekeeping force's mandate was extended to October 15, 2011.