Four people suspected of assassinating Haiti's President Jovenel Moïse have been killed in a shootout with the security forces, police say.
Two others have been detained, while some remaining suspects are thought to be still at large in the nation's capital Port-au-Prince, reports BBC.
"They will be killed or captured," police chief Leon Charles said.
Mr Moïse, 53, was fatally shot and his wife was injured when attackers stormed their home early on Wednesday.
The president was reportedly hit by multiple bullets and his office and bedroom were ransacked. First Lady Martine Moïse has been flown to Florida where she is said to be in a critical but stable condition and is receiving treatment.
"Four mercenaries were killed [and] two were intercepted under our control," Mr Charles said in a televised statement late on Wednesday. "Three policemen who had been taken hostage have been recovered."
"We blocked [the suspects] en route as they left the scene of the crime," he added. "Since then, we have been battling with them."
Speaking after the killing, interim Prime Minister Claude Joseph called for calm and declared a nationwide state of emergency.
The state of emergency, or "state of siege", allows for the banning of gatherings and use of the military for police roles, along with other extensions of executive powers.
US President Joe Biden offered condolences to the people of Haiti for the "horrific assassination". UK Prime Minister Boris Johnson, meanwhile, called it "an abhorrent act" and also appealed for calm.
The UN Security Council, which is due to hold a closed-door meeting on the killing on Thursday, issued a statement in which it made "an emphatic call on all political stakeholders in Haiti to refrain from any acts of violence or incitement".
Mr Moïse became president of Haiti in 2017, but in recent times faced widespread protests demanding his resignation.
Coups, political instability, widespread gang violence and natural disasters have plagued the country for decades and rendered it the poorest nation in the Americas.
What do we know about the shooting?
Heavily armed assassins stormed the couple's home in the hills above Port-au-Prince at around 0100 local time (0500 GMT).
Mr Joseph said the attackers were "foreigners who spoke English and Spanish". Haiti's official languages are Creole and French.
Some reports spoke of men dressed in black who carried high-powered weapons who may have pretended to be part of a US drug enforcement operation, although no official details have been given.
Haiti's ambassador to the US, Bocchit Edmond, said there was "no way" US drugs agents carried out the attack. He believed it was the work of "professional mercenaries" and later said they were disguised as agents.
Addressing the nation, Mr Joseph vowed the killers would be brought to justice and said the security situation was "under control".
Who will take control?
Mr Joseph said that "all measures have been taken to ensure continuity" and that "democracy and the republic will win".
But questions remain about how much control he can assert.
A new prime minister, Ariel Henry, was named by Mr Moïse just this week but has yet to be sworn in.
Haiti's constitution says the president of the Supreme Court should take over in the event of a presidential vacancy. However, Chief Justice René Sylvestre died of Covid-19 weeks ago.
The US said it believed elections should go ahead this year, to bring about a peaceful transfer of power.
Ruling by decree
Jovenel Moïse's time in office was rocky, as he faced accusations of corruption and there were widespread demonstrations in the capital and other cities earlier this year.
Parliamentary elections should have been held in October 2019 but disputes have delayed them, meaning Mr Moïse had been ruling by decree.
In February this year, on the day the opposition wanted him to leave office, Mr Moïse said an attempt to kill him and overthrow the government had been foiled.
Haiti has also faced a wave of gang violence and kidnappings, particularly in the capital, with a number of its districts becoming no-go areas.
The worsening living standards in the nation of 11 million people have pushed nearly 60% below the poverty line.
An earthquake in 2010 killed more than 200,000 people and caused extensive damage to the infrastructure and the economy.
A UN peacekeeping force was put in place in 2004 to help stabilise the country, and only withdrew in 2017, but the turmoil has shown no sign of ending.