Haitian President Jovenel Moise was assassinated and his wife wounded early on July 7 in a gun attack at their private residence, tipping the impoverished and crisis-hit Caribbean nation into a renewed state of political uncertainty.

Interim Prime Minister Claude Joseph declared a national “state of siege” and said he was now in charge of the country, urging people to remain calm while insisting the police and army would ensure public order.

As international outrage and shock spread over the killing, the airport was closed in the capital Port-au-Prince, but witnesses said the city was quiet on July 7 with no extra security forces on patrol.

“The president was assassinated at his home by foreigners who spoke English and Spanish,” Joseph said of the assault that took place around 1:00am (0500 GMT).

“This death will not go unpunished,” Joseph said in an address to the nation.

Moise’s wife Martine, who was to be evacuated to Miami, was being treated in a local hospital.

Haiti’s ambassador to Washington, Bocchit Edmond, told reporters the killers were “professional” mercenaries who disguised themselves as US Drug Enforcement Administration (DEA) agents and may have already left the country.

“We have a video and we believe that those are mercenaries,” he added.

Moise had ruled Haiti, the poorest country in the Americas, by decree after legislative elections due in 2018 were delayed in the wake of disputes, including on when his own term ends.

In addition to the political chaos, kidnappings for ransom have surged in recent months, reflecting the growing influence of armed gangs in the country.

Haiti also faces chronic poverty and recurrent natural disasters.

The president faced steep opposition from swathes of the population that deemed his mandate illegitimate, and he churned through a series of seven prime ministers in four years

Most recently, Joseph was supposed to be replaced this week after only three months in the post.

As well as presidential, legislative and local elections, Haiti was due to have a constitutional referendum in September after it was twice postponed due to the coronavirus pandemic.

The UN Security Council called an emergency meeting on July 8 on Haiti, while US President Joe Biden condemned the killing as “horrific” and said Washington was ready to assist in any way.

“We condemn this heinous act, and I am sending my sincere wishes for First Lady Moise’s recovery,” Biden said in a statement.

UN secretary-general Antonio Guterres called on Haitians to “remain united in the face of this abhorrent act and reject all violence”, his spokesman said.

Just hours after the assassination, Joseph announced he had declared a “state of siege”, which grants the executive additional powers. Haiti will mark two weeks of national mourning from July 8.

EU foreign policy chief Josep Borrell warned “this crime poses a risk of instability and a spiral of violence. The perpetrators of this assassination must be found and brought to justice”.

Moise – a 53-year-old former entrepreneur who set up a string of businesses in the north of the country, where he hails from – burst onto the political stage in 2017 with a message of rebuilding the impoverished nation.

He campaigned on populist pledges, and was sworn in in February 2017.

The end date of his mandate became the source of a political standoff.

Moise maintained that his term of office ran until February 7, 2022, but others claimed it ended on February 7, 2021.

The disagreement stems from the fact that Moise was elected in a 2015 vote that was cancelled for fraud, and then re-elected in November 2016.

Without a parliament, the country fell further into crisis in 2020, and led to Moise governing by decree, fuelling growing mistrust of him.