The UN Security Council expressed its concern over the deteriorating situation in violence-gripped Haiti on Wednesday, as Washington ramped up pressure on absent Prime Minister Ariel Henry to secure a political settlement.

Armed gangs who control swaths of the country launched a coordinated effort to oust Henry last week, attacking the airport, prisons and police stations, while threatening a full-scale civil war.

The United States on Wednesday called for Henry to take steps to "finalize a political accord," but did not urge his resignation -- a key demand of powerful gang leader Jimmy "Barbecue" Cherizier.

In power since the 2021 assassination of president Jovenel Moise, Henry was due to leave office in February but instead agreed to a power-sharing deal with the opposition until new elections are held.

Cherizier warned Tuesday that the worsening chaos would lead to civil war and mass bloodshed unless Henry stood down.

At least 15,000 people have fled the worst-hit parts of Port-au-Prince.

One displaced man told AFP on Wednesday that he had been forced to flee after a gang attack.

"In my case, I ran away from my house, abandoning everything I own," Jhonnyy Desmion said.

United Nations rights chief Volker Turk said Wednesday the situation was "beyond untenable" with 1,193 people killed countrywide this year by gang violence.

Malta's UN ambassador Vanessa Frazier said that every Security Council member "shared the same concerns, that the security situation is obviously concerning."

Amid the latest unrest, Henry has been unable to return home.

He was in Kenya to push for the deployment of a UN-backed multinational police mission to help stabilize his country when the attempt to oust him began.

"The situation requires" the deployment of a mission as soon as possible, Ecuador's UN ambassador Jose Javier De La Gasca Lopez-Dominguez said.

Gunfire has shut down some flights at Toussaint Louverture International Airport, and Henry was denied permission to land in neighboring Dominican Republic on Tuesday.

He later touched down in the US territory of Puerto Rico, a spokesperson for the island's governor said, although it was not clear how long he would stay.

Regional Caribbean bloc CARICOM warned that the spiraling crisis was "compounded by the absence of key institutions functioning, such as the presidency and the parliament."

"There must be a political solution to anchor any stabilization of security and humanitarian efforts," said Mohamed Irfaan Ali, Guyana's president and the current chairman of CARICOM.

- Gangs rule the streets -

Haitian officials have been pleading for months for international assistance to help their overwhelmed security forces, as gangs push beyond the capital city and into rural areas.

The government has declared a state of emergency and a nighttime curfew, which has been extended through Wednesday.

As the evening drew in, heavily-armed security forces wearing ballistic helmets stood guard at key points in Port-au-Prince, which was quieter than usual.

"We have no authorities, no leaders, we have no one, we have nothing," Linda Antoine, a shopkeeper in the city told AFP. "It's every man for himself." 

Citing the "rapidly deteriorating security situation," UN Secretary-General Antonio Guterres had called this week for urgent financial support for the multinational police mission.

"Hundreds of thousands of children and families are displaced and cut off from lifesaving services and aid as armed groups rule the streets," Catherine Russell, head of UNICEF, said Tuesday. "The world must not stand idle."

Haiti, the Western hemisphere's poorest nation, has been in turmoil for years, and Moise's assassination plunged the country further into chaos.

No elections have taken place since 2016 and the presidency remains vacant.

Although there is rising pressure on Henry from the United States, "we are definitely not pushing for the prime minister to resign," White House Press Secretary Karine Jean-Pierre told reporters.

"But we have underscored that now is the time to finalize a political accord to help set Haiti on a path to a better future."

She added the United States would not assist Henry to return to his country, or discuss his travels.

Between violence, the political crisis and years of drought, some 5.5 million Haitians -- about half the population -- need humanitarian assistance.

After months of delays, the UN Security Council finally gave its greenlight in October for a multinational policing mission led by Kenya.

But that deployment has been stalled by Kenyan courts.

Nairobi and Port-au-Prince signed a bilateral agreement on Friday on the mission, but it remains without a firm start date.