PORT-AU-PRINCE (Reuters) -The United States called for its citizens to leave Haiti "as soon as possible" after violence escalated late last week, when 15,000 more people fled the fighting and armed men broke thousands of inmates from Haiti's largest prison.

The United States, which is home to over a million Haitians, said its embassy would be offering limited operations on Monday while Canada said it would temporarily close its embassy.

This follows the Haitian government's declaration of a state of emergency on Sunday evening after violent clashes in the capital damaged communications and led to a prison escape as the leader of the major G9 gang alliance sought to oust the prime minister.

Later on Monday, hundreds of people, reportedly escaped inmates, gathered in the capital chanting for Prime Minister Ariel Henry to step down, and their support for Johnson "Izo" Andre, a leader of a gang linked to the capital's other main gang alliance, G-Pep.

The Organization of American States (OAS) said it was deeply concerned and said it was necessary to promote cooperation with the United Nations to restore security: "It is irresponsible that the necessary measures and actions continue to be delayed."

The U.N. last October ratified a plan to send an international force, based on voluntary contributions from member states, to help Haitian police restore security - a year after Prime Minister Ariel Henry first requested this.

There is currently no deployment date, and as of the end of February the United Nations said five nations had formally pledged troops - The Bahamas, Bangladesh, Barbados, Benin and Chad - and less than $11 million were deposited in its fund.

The largest public pledges for personnel come from Benin, which offered 1,500 people according to the U.N., and Kenya which late last week sealed a deal with Henry to lead the mission with some 1,000 police officers, after legal setbacks.

Haiti's national police is down by over 3,000 officers in the last three years, according to its union, with many calling for stronger protections, better equipment and better pay amid the deadly clashes with gangs armed with assault weapons, believed to be largely trafficked from the United States.

Between Thursday and Saturday last week, the United Nations estimated close to 15,000 people were forced to flee, including those already in makeshift camps for displaced people set up in schools, hospitals and squares around the capital.

The U.N. estimated earlier this year over 300,000 had fled their homes due to the worsening gang conflict, which saw close to 5,000 killed last year.

Aid groups, faced with under-funded campaigns, have urged the force to prioritize securing routes for providing people with medical care and food, as the U.N. warns that millions of people are facing acute hunger.

(Reporting by Sarah Morland and Harold Isaac; Editing by Kylie Madry and Chizu Nomiyama)