GENEVA - The United Nations peacekeeping mission in Haiti must tackle criminal gangs boosted by the escape of thousands of prisoners after the country's devastating quake, an UN spokesman said Friday.

"It is clear that MINUSTAH must go back to zero with the work that it had accomplished in the last three years in order to face the gangs in Haiti," said Corinne Momal-Vanian, a UN spokeswoman.

She added, however, that the "security situation is stable despite some isolated incidents."

"Security has always been a problem in some areas of Port-au-Prince... but the situation is under control, even in the areas such as Cite Soleil and Martissant, where United Nations troops and the Haitian police are patrolling daily," she said.

Some 5,000 of the 8,000 prisoners held in the main Port-au-Prince jail escaped after the January 12 quake which killed more than 200,000 people.

Edmond Mulet, acting head of the UN's Stabilisation Mission in Haiti (MINUSTAH) was concerned that gang leaders were seeking to reorganise in order to take control of areas of the city, she added.

"According to information received, none of them have however been able to resume drug trafficking activities, but some clashes between gangs had been reported," said Momal-Vanian.

A call by UN Secretary General Ban Ki-moon, who had promised to deploy 3,500 additional UN personnel in Haiti, had resulted in "sufficient offers of troops," she said.