The death toll from an attack by Islamist militants on a hotel in the Somali capital rose to at least 15, police said as fighting continued into early Saturday, with loud explosions heard overnight.

Al Shabaab fighters blasted and shot their way into the popular Hotel Maka Al Mukaram on Friday afternoon, trapping many government officials.

Security personnel, led by a unit from the elite U.S.-trained special forces troops known as "Gaashaan" (Shield) stormed the hotel on Friday evening and fought the attackers into Saturday.

"At least 15 people died including Somalia's ambassador to Geneva, and at least 20 others were wounded," Colonel Farah Aden, a senior police officer at the scene, told Reuters.

"Those who died include civilians, hotel guards and government soldiers."

Abdiasis Abu Musab, al Shabaab's military operations spokesman, said they had targeted only government officials.

"We killed those who belonged to the government and released the civilians," he told Reuters by phone.

Journalists and paramedics were barred from entering the hotel grounds on Saturday and were only allowed to watch from its gate. A Reuters photographer said the siege seemed to have subsided, with security forces searching the rooms for fighters and booby traps.

Streets surrounding the hotel were sealed off by government and African Union peacekeeping troops.

Al Qaeda-linked al Shabaab was pushed out of the capital by African peacekeeping forces in 2011, but has kept up guerrilla-style attacks, looking to overthrow the government and impose its strict version of Sharia, or Islamic law, on the country.

An offensive launched last year by African Union forces along with the Somali army has driven the group out of its strongholds in central and southern Somalia, while a series of U.S. drone strikes have killed some of its top leaders.