A gang attack in Port-au-Prince forced residents to flee their homes as the gangs operating in and around the Haitian capital ramp up attacks on areas they don't yet control.

Smoke from gunfights billowed above the capital's Solino neighbourhood on Saturday, where fleeing residents strapped mattresses, furniture, cooking supplies and other possessions to trucks.

Others fled on foot, carrying what belongings they could.

(The number of displaced people in Haiti has doubled in the past three months to almost 700,000. (AP PHOTO)

Gangs have been escalating their attacks on a number of towns in and around the capital, where much of the city and its suburbs are under the control of various violent armed groups united under a common alliance known as Viv Ansanm.

In Solino, thousands of residents have been displaced in recent days, including people who had previously been displaced from other neighbourhoods, the UN's World Food Programme (WFP) said in a press conference on Friday.

The total number of displaced people in Haiti has doubled in the past three months to almost 700,000, the WFP said.

Haiti's security crisis continues to fuel the Caribbean nation's humanitarian disaster.

The World Food Programme said on Friday that 5.4 million Haitians, or roughly half of the population, is suffering from acute hunger, with pockets of famine-level hunger being reported among internally displaced people.

A UN helicopter aiding humanitarian efforts was hit by gunfire on Thursday while flying over Port-au-Prince, later landing safely, the WFP said.

While the UN authorised an international force to help Haiti's police take back control from the gangs, the mission has been poorly resourced and has produced scant results.

Port-au-Prince