The gang leader behind the violence blighting the Haitian capital has warned there will be a "civil war" if Haiti's prime minister, Ariel Henry, does not step down.
Jimmy "Barbecue" Chérizier made the threat as members of his gang tried to seize the capital's airport to stop Mr Henry from returning from abroad.
The UN High Commissioner for Human Rights Volker Türk said the situation was "beyond untenable".
Thousands of Haitians have had to flee.
Aid groups say about 15,000 people, among them many young children, have been displaced from their homes in recent weeks.
Mr Türk said that since the beginning of the year, "a staggering 1,193 people have been killed, and 692 others injured by gang violence".
He urged the international community to "act swiftly and decisively to prevent Haiti's further descent into chaos".
The United States has called on Mr Henry to "expedite" a transition.
US State Department spokesman Matthew Miller urged a transition to prepare for "a multinational security support mission" and to "pave the way for free and fair elections".
He said that the US wanted Mr Henry to "make concessions in the interest of the Haitian people" but added that Washington was not "pushing for him to resign".
Mr Henry's whereabouts had been unknown for days until late on Tuesday, when he boarded a charter flight in New Jersey.
Heavily armed Puerto Rico police guard the U.S. Customs and Border Protection office while Haiti's Prime Minister Ariel Henry is inside after he arrived at Luis Munoz Marin International Airport in San Juan, Puerto Rico, March 5, 2024.
Reports said Mr Henry had planned to land in the Haitian capital of Port-au-Prince, but with the airport closed due to the gangs' attempts to seize it, and neighbouring Dominican Republic turning the plane away, the pilot eventually landed in the US territory of Puerto Rico.
Haitian media report that Mr Henry is now seeking alternative routes back into the country while diplomatic pressure appears to be mounting on him to agree to a transitional government.
Meanwhile, tension remains high in Haiti, with Jimmy "Barbecue" Chérizier warning on Tuesday that "if Ariel Henry does not resign ... we'll be heading straight for a civil war that will lead to genocide".
The G9 alliance which he leads has unleashed a wave of violence, including attacks on police stations and the storming of the country's two main prisons. Thousands of inmates escaped in a mass jailbreak on Saturday.
How gangs came to dominate Haiti
Haiti has been blighted by gang violence for years. But while Prime Minister Henry was on a visit to Kenya last week, Barbecue escalated the situation.
Mr Henry was aiming to agree a deal for Kenya to lead a multinational police operation to quell the violence in Haiti.
Barbecue fears Mr Henry would use the forces to stay in power.
The gang leader has been opposed to the prime minister since he took over power shortly after the assassination of President Jovenel Moïse in July 2021, without an election.
Critics of Mr Henry argue his rule is illegitimate. They also point to the fact that two and a half years after coming to power he has still not organised presidential elections, as he had originally promised.
The prime minister has not spoken publicly since the violence erupted. He has only retweeted the declaration of the state of emergency decreed by one of his ministers in his absence.
It is not clear what gang leader Barbecue's longer term aims are. On Tuesday he urged Haitians "to unite".
"Either Haiti becomes a paradise for all of us, or a hell for all of us," he told journalists, wearing a bullet-proof vest.
In the past he has suggested creating a "council of elders", a group of civil society representatives from different regions, to replace the prime minister.
Haiti has no elected government officials. No elections have been held since 2016 in the country.
The vacuum created by the lack of elected officials has been filled by gangs, who are estimated to control around 80% of the capital.
Kidnappings for ransom are common and many schools and hospitals have had to close due to the lack of security.
The UN's Chief Humanitarian Coordinator in Haiti, Ulrika Richardson, told the BBC's Newshour programme that "people are very afraid".
Ms Richardson said violence was being used "indiscriminately against people, against women, against children and that includes sexual violence".
"We see cadavers in the streets, we hear direct accounts of the atrocities that women and many children have been exposed to," she told the BBC.
Violence has so far been mainly concentrated in the capital and its environs. But there have also been reports of shootings in the town of Jeremie, in the south west, and of a prison riot in Jacmel in the south.
The United Nations Security Council said it would hold an emergency meeting later on Wednesday to discuss the violence.
Haiti: The basics
Population: 11.5 million (estimate)
Area: 27,800 sq km (slightly smaller than Belgium, about the same size as the state of Maryland in the US)
Location: Caribbean country sharing a border with the Dominican Republic
Languages: French, Haitian Creole
Source: BBC
BDST: 0913 HRS, MAR 07, 2024
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