(LONDON) — Haitian President Jovenel Moise was killed in an attack at his home before dawn on Wednesday, the country’s interim premier said.

A group of unidentified individuals raided Moise’s private residence in Haiti’s capital, Port-au-Prince, at around 1 a.m. local time. They gunned down the 53-year-old head of state and wounded his wife, Martine Moise, who remains hospitalized, according to a statement from Haitian interim Prime Minister Claude Joseph.

Joseph, who condemned what he called a “hateful, inhumane and barbaric act,” said that the Caribbean country’s national police force and military had the situation under control and declared a state of emergency.

Late Wednesday, Haiti’s communications secretary said in a tweet that police have arrested the “presumed assassins,” but Frantz Exantus did not provide further details about Wednesday’s slaying or say how many suspects had been arrested. He said more information was forthcoming.

Reaction has been pouring in from around the world condemning the assassination, including from U.S. President Joe Biden, who called the situation “very worrisome.”

Reeling from the coronavirus pandemic, Haiti has also been in the midst of a constitutional crisis as Moise and opposition leaders disputed the end of his five-year presidential term and legislative elections remained interminably delayed.

Addressing the nation in a televised speech, Joseph called on the people of Haiti to “stay calm.” He chaired a meeting of the government’s ministers Wednesday morning, although the country’s line of succession is unclear, especially given its recent political turmoil.

“All the ministers and I have been working since the news broke and we want to assure you we will bring the killers of the president to justice,” he said. “Please stay calm and let the authorities do their work. We don’t want the country to plunge into chaos. This is a very sad day for our nation and for our people.”

The assailants, who remain at large, were “well-trained commandos” who were speaking Spanish and most likely came from outside Haiti, according to Bocchit Edmond, Haiti’s ambassador to the U.S. The group was “highly trained and heavily armed,” according to Joseph, who called for an urgent United Nations Security Council meeting and an international investigation into the attack.

Edmond said the Haitian government had video evidence of the group speaking Spanish. He also said they claimed to be agents from the U.S. Drug Enforcement Administration, which Edmond rejected. He urged the U.S. to provide security assistance not just for the immediate investigation, but also to boost Haitian security forces against armed gangs and a porous border.

First lady Martine Moise is in stable but critical condition, according to Edmond, and she was to be moved to a Miami hospital for treatment at some point Wednesday.

The streets of Haiti’s capital Port-au-Prince were largely deserted Wednesday and Toussaint Louverture International Airport has been closed in the wake of the assassination.

The U.S. Embassy in Port-au-Prince was also closed Wednesday, including for consular services, “due to an ongoing security situation,” it said in a security alert. The embassy also said it is restricting its American staff to its compounds “until further notice” and urged members of the public to avoid unnecessary travel to the area.

U.S. officials are “still gathering information” on the deadly attack, according to White House press secretary Jen Psaki, offering U.S. assistance “if there’s an investigation.”

“We’re still assessing, still gathering information, and the president of course will be briefed by his national security team this morning,” she said.

Hours later, the White House issued a statement from Biden condemning “this heinous act.”

“I am sending my sincere wishes for First Lady Moïse’s recovery. The United States offers condolences to the people of Haiti, and we stand ready to assist as we continue to work for a safe and secure Haiti,” the statement said.

Haiti has been in a state of chaos for months now, with frequent gunfire and street skirmishes between armed groups, political demonstrations and strikes, and a coronavirus wave never brought under control. Cases of the virus were as high last month as they were one year ago, and the country has yet to distribute a single vaccine dose or receive any shipments from COVAX, the international program to provide vaccines to low- and middle-income countries.

That’s in part because of the governing crisis roiling Haiti. The country’s political opposition had argued that Moise’s five-year presidential term ended this February — five years after his election victory, but four years after he took office — while he said he had one more year left because the disputed 2016 election delayed his inauguration until 2017.

Moise had been governing by decree since January 2020, after the country failed to hold legislative elections and the legislature’s mandate expired. Opposition leaders accused him of wanting to return Haiti to a dictatorship.

Earlier this year, Moise ordered the retirement of three Supreme Court judges and the arrest of nearly two dozen people, including prominent officials, who he alleged were plotting a coup. Violent protests against Moise erupted, prompting the president to declare a state of emergency in parts of the country in March.

The political instability in addition to economic woes and escalating gang violence have undermined efforts to rebuild Haiti from a devastating earthquake in 2010 and Hurricane Matthew in 2016.

While the Biden administration backed Moise’s claim to have one more year in office, it had grown increasingly vocal in its opposition to his “one-man rule,” in the words of the top U.S. diplomat for the Western Hemisphere, including governing by decrees and refusing to hold those legislative elections.

While the White House has said it will provide Haiti some of the initial 80 million COVID-19 vaccines it has promised to share overseas, it has yet to announce when it will do so — with the worsening security situation now making it that much harder.

ABC News’s Christine Theodorou, Molly Nagle, and Sarah Kolinovsky contributed to this report.

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