PORT-AU-PRINCE - Heavy gunfire erupted early Saturday in the Haitian capital as residents, already enduring chaotic violence and grave food shortages, faced mounting frustration over delays in announcing a transitional government meant to restore stability.

Residents contacted by AFP said armed criminals had attacked a base of the Departmental Operation and Intervention Brigade (BOID), a rapid-reaction force, in the Fort Nationale neighborhood of Port-au-Prince.

Another specialized unit in the capital area, the Motorized Intervention Brigade (BIM), was also attacked, locals said.

There were no immediate details of casualties.

The scenes of chaos played out as the impoverished Caribbean country continued a tense wait for the establishment of a transitional government -- part of a deal that brought the promised resignation of unpopular Prime Minister Ariel Henry.

Henry agreed on March 11 to step down, but negotiations on forming a transitional government have been slow despite pressure from neighboring Caribbean countries and the United States.

The political chaos and street violence are taking place against a backdrop of increasingly desperate hunger.

Farhan Haq, a spokesman for the UN secretary-general, said roughly half the Haitian population face "crisis or worse levels of acute food insecurity."

Haiti has been rocked by violence for weeks, starting with the coordinated gang offensive to release thousands of prison inmates.

Amid the sharply worsening conditions, more than 33,000 people have fled the capital area in the past two weeks, according to the UN International Organization for Migration.

Many foreigners have fled the country, and the US Embassy has been evacuating any American citizens hoping to leave.

The State Department said Friday evening that it had helped 230 citizens to leave since March 17.

And it renewed a blunt warning to US citizens: "Do not travel to Haiti."