Haiti's government declared a state of emergency and nighttime curfew late Sunday in a bid to regain control of the streets after an explosion of violence over the weekend saw armed gang members storm the country's two biggest prisons.

The 72-hour state of emergency went into immediate effect as the government said it would set out to find the killers, kidnappers and other violent criminals that it reported escaped from the prison.

“The police were ordered to use all legal means at their disposal to enforce the curfew and apprehend all offenders,” said a statement from Finance Minister Patrick Boivert, who is serving as acting prime minister.

Prime Minister Ariel Henry travelled abroad last week to try to salvage support for a bringing in a United Nations-backed security force to stabilise the country in its conflict with increasingly powerful crime groups.

The decree capped a deadly weekend that marked a new low in Haiti's downward spiral of violence. At least nine people had been killed since Thursday — four of them police officers — as gangs stepped up coordinated attacks on state institutions in Port-au-Prince. Targets included police stations, the country's international airport, even the national soccer stadium.

But the siege on Saturday night of the National Penitentiary came as a shock even to Haitians accustomed to living under the constant threat of violence. Almost all of the estimated 4,000 inmates fled during the jailbreak, leaving the normally overcrowded facility eerily empty Sunday with no guards in sight and plastic sandals, clothing and furniture strewn across the concrete patio. Three bodies with gunshot wounds lay at the prison entrance.

In another neighbourhood, the bloodied corpses of two men with their hands tied behind the backs lay face down as residents walked past roadblocks set up with burning tires.

Among the few dozen that chose to stay in the prison are 18 former Colombian soldiers accused of working as mercenaries in the July 2021 assassination of Haitian President Jovenel Moïse. Amid the clashes Saturday night, several of the Colombians shared a video pleading for their lives.

“Please, please help us,” one of the men, Francisco Uribe, said in the message widely shared on social media. "They are massacring people indiscriminately inside the cells.”

On Sunday, Uribe told journalists who walked breezily into the normally highly guarded facility, “I didn't flee because I'm innocent."

Colombia's foreign ministry called on Haiti to provide “special protection” for the men.

In the absence of official information, inmates' family members rushed to the prison to check on loved ones.

“I don't know whether my son is alive or not,” said Alexandre Jean as she roamed around the cells looking for any sign of him. “I don't know what to do.”

The violence Saturday night appeared to be widespread, with several neighbourhoods reporting gunfire.

A second Port-au-Prince prison containing around 1,400 inmates was also overrun. Gang gunmen also occupied and vandalised the nation's top soccer stadium, taking one employee hostage for hours, Haiti's soccer federation said in a statement.

Internet service for many residents was down as Haiti's top mobile network said a fibre optic cable connection was slashed during the rampage.

In the space of less than two weeks, several state institutions have been attacked by the gangs, which are increasingly coordinating their actions and choosing once unthinkable targets like the Central Bank. As part of coordinated attacks by gangs, four police officers were killed Thursday.

After gangs opened fire at Haiti's international airport last week, the US Embassy said it was halting all official travel to the country and on Sunday night urged all American citizens to depart as soon as possible. The embassy said it would also cancel until Thursday all consular appointments.

The Biden administration, which has steadfastly refused to commit troops to any multinational force while offering instead money and logistical support, said it was monitoring the rapidly deteriorating security situation with grave concern.

A National Security Council official said violence serves only to delay a democratic transition while destroying the lives of thousands. The official, who spoke on condition of anonymity, reiterated US support for elections, inclusive governance and the restoration of democracy.

The epicentre of the latest violence Saturday night was Haiti's National Penitentiary, which was holding several gang leaders. Amid the exchange of gunfire, police appealed for assistance.

“They need help,” a union representing police said in a message on social media bearing an “SOS” emoji repeated eight times. “Let's mobilize the army and the police to prevent the bandits from breaking into the prison.”

The clashes follow violent protests that turned deadlier in recent days as the prime minister went to Kenya seeking to move ahead on a proposed UN-backed security mission in Haiti to be led by that East African country.

Henry took over as prime minister following Moise's assassination and has repeatedly postponed plans to hold parliamentary and presidential elections, which haven't happened in almost a decade.

Haiti's National Police has roughly 9,000 officers to provide security for more than 11 million people, according to the UN. They are routinely overwhelmed and outgunned by gangs, which are estimated to control up to 80 per cent of Port-au-Prince.

Jimmy Chérizier, a former elite police officer known as Barbecue who now runs a gang federation, has claimed responsibility for the surge in attacks. He said the goal was to capture Haiti's police chief and government ministers and prevent Henry's return.

The prime minister, a neurosurgeon, has shrugged off calls for his resignation and didn't comment when asked if he felt it was safe to come home.