The UN Security Council on Thursday voted to reduce the UN peacekeeping mission in Haiti which is battling a mounting controversy over a cholera epidemic.

One day after a lawsuit against the United Nations was filed in a New York court on behalf of victims, the Security Council urged the UN to support government efforts to battle the epidemic.

The epidemic has killed more than 8,300 people since it started in October 2010 and made more than 679,000 sick. It has been traced to a river next to a UN camp where Nepalese troops were based.

A Security Council resolution which extended the mandate of the UN mission in Haiti, MINUSTAH, noted government efforts to "control and eliminate" the epidemic.

It urged "United Nations entities in coordination with other relevant actors to continue to support the government of Haiti in addressing the structural weaknesses, in particular in the water and sanitation systems" in the impoverished Caribbean nation.

The resolution also acknowledged "United Nations efforts to combat cholera" including through a $2.2 billion appeal launched by UN leader Ban Ki-moon to counter the epidemic.

It said there should be support for "rapid and targeted medical responses to outbreaks designed to reduce the threat" from the cholera.

The Security Council reduced the maximum size of MINUSTAH to 5,021 troops, down from 6,233, and 2,601 police from 2,457. The reduction is part of a general campaign to cut UN forces where the security threat has fallen away.

But the UN faces a prolonged battle over MINUSTAH which was originally sent to end political strife in 2004 and also played a key role after the January 2010 earthquake which killed more than 250,000 people.

Lawyers from the US-based Institute for Justice and Democracy in Haiti (IJDH) filed a lawsuit in New York on Wednesday seeking compensatiion from the United Nations.

The lawyers have previously sought $100,000 for the family of each victim who died and $50,000 for each survivor.

Medical studies have increasingly pointed to a UN link to the cholera. The strain in Haiti is one that is commonplace in Nepal.

But the United Nations said in February that the legal complaint was "non-receivable" under a 1946 convention setting out the UN's immunities for its actions.

The UN has since refused to comment on the court case, which in a worst case scenario could cost billions.

"The UN remains committed to do all it can to help the people of Haiti overcome the cholera epidemic," a UN spokesman, Farhan Haq, said Wednesday when asked about the damages claim.

UN Secretary General Ban launched a $2.2 billion appeal in December to provide clean water and health facilities in Haiti.