Haiti has declared a state of emergency after the assassination of its president Jovenel Moïse, who was shot dead during the night in his private home on the outskirts of the capital Port-au-Prince.

“At around 1am . . . a group of unidentified individuals, some of whom were speaking Spanish, have attacked the president of the republic’s private residence and mortally wounded the head of state,” interim prime minister Claude Joseph said in a statement. He later said the killers had also spoken in English.

Joseph appealed to the Caribbean nation’s 11m population for calm and condemned what he called an “odious, inhuman and barbaric act”, in which Moïse’s wife Martine was also seriously wounded. Haiti’s ambassador to the US, Bocchit Edmond, told reporters the first lady is in critical condition and that efforts are being made to fly her to Miami for treatment.

The government later added in a statement: “Although details are still emerging, at this time it can be confirmed that this was a well-co-ordinated attack by a highly trained and heavily armed group”.

The president’s murder prompted international condemnation and concern. US president Joe Biden described the situation in Haiti as “very worrisome” and said Washington stood ready to help. UN secretary-general António Guterres called on Haitians to “remain united in the face of this abhorrent act” and preserve the constitutional order. The Organization of American States condemned an “affront” to the “community of democratic nations”.

Various videos were circulating online purporting to show a group of heavily armed commandos attacking Moïse’s residence during the night. Their authenticity could not be verified.

Joseph has called on the UN security council to discuss the situation in Haiti as soon as possible. He claimed that Haiti’s security forces had the situation in hand, and moved quickly to assert control amid questions over who was in charge. Moïse had named a new prime minister, Ariel Henry, only two days before he was killed, but Henry had not yet taken office.

“I have just presided over an extraordinary council of ministers meeting and we have decided to declare a state of emergency in the whole country,” Joseph said.

“The streets are very quiet. Everyone is staying at home and waiting,” said one foreign businessman in Port-au-Prince. “But there’s a big concern over what happens next. Most of the opposition is as bad or worse than this guy was.”

The neighbouring Dominican Republic, which shares the island of Hispaniola with Haiti, closed the border between the two nations. Its president Luis Abinader called an emergency meeting.

Moïse, a former banana exporter turned politician, had been ruling by decree since October 2019 when parliamentary elections were scrapped. His legitimacy was repeatedly questioned, with the opposition and many legal experts arguing that his presidential term had expired.

Mass protests over allegations of government corruption and involvement in gang violence punctuated his time in office, although he consistently denied involvement.

Haiti, the poorest country in the Americas, has suffered repeated political and economic crises in recent years, as well as several natural disasters. It has struggled to rebuild since a devastating earthquake in 2010 and Hurricane Matthew in 2016.

Food and fuel shortages have plagued the country, and increasing lawlessness has scared away investors and much of the middle class. Transparency International rated the country 170th out of 180 in its global corruption perceptions index last year. The World Bank says that nearly 60 per cent of the population live in poverty.

Jake Johnston, an expert at the Center for Economic and Policy Research in Washington who recently visited Port-au-Prince, described Haiti as a “terrifying situation, not just because of [the assassination] but because of the broader situation of insecurity and violence, with more than a dozen massacres perpetrated in Port-au-Prince over the last three years by current and former police with impunity, the dismantling of state institutions and the lack of government legitimacy”.

Moïse had planned to hold fresh elections and a constitutional referendum in September, but the opposition had questioned whether these could be free and fair, given the dire situation.

A group of US lawmakers wrote to Antony Blinken, secretary of state, in April expressing “serious and urgent” concern over the deteriorating situation and saying the Moïse government was “failing to meet even the most basic needs of its citizens”. It called on the US government to work with Haitian civil society to ensure that elections met international standards.