Gunmen posing as military forces held an unknown number of hostages inside a popular restaurant in Somalia's capital in an attack that left 14 people dead and began when a car bomb exploded, police and a witness said Wednesday night.

The extremist group al-Shabab claimed responsibility. Police said those killed included foreigners.

Two of the gunmen were shot dead and 10 hostages were rescued, but five other attackers were thought to remain inside, cutting off electricity to complicate security forces’ efforts to end the siege, Capt. Mohamed Hussein said. He said heavy gunfire was heard.

Police said at least 14 people, including a Syrian man, had been killed and several others wounded. Most of the victims were young men who had been entering the Pizza House when the vehicle exploded, Hussein said.

The gunmen "were dressed in military uniforms. They forced those fleeing the site to go inside” the restaurant, witness Nur Yasin told the Associated Press.

The blast largely destroyed the restaurant’s facade and sparked a fire. While al-Shabab claimed to have attacked the neighboring Posh Treats restaurant, which is frequented by the city’s elite and was damaged in the blast, security officials said the Pizza House was targeted instead.

Security forces rescued Asian, Ethiopian, Kenyan and other workers at Posh Treats as the attack continued, Hussein said.

The Somalia-based al-Shabab often targets high-profile areas of Mogadishu, including hotels, military checkpoints and areas near the presidential palace. It has vowed to step up attacks after the recently elected government launched a new military offensive against it.

Al-Shabab last year became the deadliest Islamic extremist group in Africa, with more than 4,200 people killed in 2016, according to the Washington-based Africa Center for Strategic Studies.

The extremist group also faces a new military push from the United States after President Trump approved expanded operations, including airstrikes, against al-Shabab. On Sunday, the U.S. military in Africa said it carried out an airstrike in southern Somalia that killed eight Islamic extremists at a rebel command and logistics camp.