TRIPOLI, Libya (AP) — In the latest sign of Libya’s descent into chaos, gunmen stormed a luxury hotel used by diplomats and businessmen in the capital on Tuesday, killing 10 people, including an American, a French citizen and three people from Asia.

Two attackers were killed following an hourslong standoff that included a car bomb that exploded in the parking lot of the seaside Corinthia Hotel. It was unclear if other gunmen were involved in the attack, which also killed five Libyan guards.

In Twitter posts and a statement on social media, a Tripoli affiliate of the Islamic State group was said to be behind the attack, but there was little evidence to back up the claims in a country that has been awash in armed extremist groups who would be equally suspect.

The SITE intelligence group reported that the two dead gunmen were identified online as sympathizers of IS and said the militants said the hotel was targeted because it houses diplomatic missions and “crusader” security companies. However, The Associated Press was unable to independently confirm the claims, which didn’t conform with the group’s earlier postings from Libya.

Militants claiming the attack on behalf of a group called the Islamic State of the Tripoli Province posted a brief video showing burned cars in the hotel’s parking lot and said it was to avenge the 2013 abduction by American commandos of a Libyan al-Qaida operative, Nazih Abdul-Hamed al-Ruqai, also known as Abu Anas al-Libi. Al-Ruqai died earlier this month in a New York hospital of complications from liver surgery while awaiting trial for the 1998 bombings of the U.S. embassies in Kenya and Tanzania.

The assault highlights the growing threat from militant groups that operate with near impunity in a country torn between rival governments since the 2011 toppling and killing of dictator Moammar Gadhafi.

Since Gadhafi’s ouster, the country has been torn among competing militias and tribes vying for power. Libya’s post-Gadhafi transition has collapsed, with two rival governments and parliaments – each backed by different militias – ruling in the country’s eastern and western regions.

Amid the bloody political rivalry, multiple armed groups have emerged, including radical Islamist militias who have pledged allegiance to the Islamic State, including one based in the eastern city of Derna, a stronghold of radical groups, as well as regional militias and groups loyal to the former regime.

Tripoli, which has been controlled by Islamist militiamen mostly from the western city of Misrata since the summer, has been hit with a series of car bombs and shootings. The internationally recognized government has been forced to relocate to the country’s east, where a former general has waged an offensive against Islamist militias, including Ansar al-Shariah, blamed for the 2012 attack on the U.S. diplomatic mission in Benghazi that left the U.S. ambassador and three other Americans dead.

A senior U.S. State Department official confirmed that a U.S. citizen was among those killed in Tuesday’s attack, but did not provide further details. Cliff Taylor, the CEO of a Virginia security company, Crucible LLC, identified the slain American as David Berry, a contractor with his company.

A French national and three citizens of a former Soviet republic were also among the dead, according to a spokesman for a Tripoli security agency, Essam al-Naas.

The Malta-owned Corinthia hotel, among the most luxurious in Tripoli, is frequented by diplomats and foreign businessmen visiting Libya, and is also where the United Nations support mission in Libya usually holds its meetings. The mission is currently hosting political talks with rival Libyan groups in Geneva, trying to resolve the country’s political and security crisis.

The hotel had Italian, British and Turkish guests but was largely empty at the time of the attack, according to hotel staff members. There was also a visiting American delegation.

The militia-backed government in Tripoli said the target was Prime Minister Omar al-Hassi, who normally resides at the hotel but was not there at the time of the attack. Spokesman Amr Baiou told reporters al-Hassi was unharmed.

A security official in Tripoli, Omar al-Khadrawi, said initial investigations pointed to a group of former Gadhafi loyalists.

Reports about how the attack unfolded were conflicting and it was not immediately possible to reconcile the different accounts.

Hotel staffers initially said that five masked gunmen stormed the Corinthia after security guards at the hotel’s gate tried to stop them, firing randomly at the staff in the lobby as guests fled out the hotel’s back doors into the parking lot.

One staffer said a car bomb exploded in the parking lot after a protection force entered the lobby and opened fire on the gunmen. Two guards were immediately killed, according to the staffer, who spoke on condition of anonymity because he feared being targeted by militants.

The car bomb incinerated at least five cars in the parking lot and damaged windows in the hotel’s facade, he said.

Al-Naas, the security agency spokesman, said after a standoff of several hours, the attackers threw a grenade at the security forces on the hotel’s 24th floor, killing themselves and a security guard. Ten people were also wounded in the attack, including security guards and guests.

“The operation is over,” al-Naas said but added that the streets around the Corinthia remained closed. He said an investigation was underway and the car used by the gunmen is believed to be the same one used in an assault on the Algerian embassy 10 days ago that wounded three guards.

The U.N. Security Council condemned the attack “in the strongest terms” and urged all countries to help bring “the perpetrators, organizers, financiers and sponsors of these reprehensible acts of terrorism to justice.” In a statement approved by all 15 members, the council also urged all parties in Libya “to engage constructively” with U.N. envoy Bernardino Leon and resume “an inclusive political process aimed at addressing the political and security challenges” facing Libya.

The Corinthia previously came under attack in 2013 when gunmen abducted then prime minister Ali Zeidan, who was living there. He was released several hours later.

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Associated Press writers Sarah el-Deeb in Cairo and Edith M. Leder at the United Nations contributed to this report.