HOMS, Syria - With a gigantic explosion, Syrian rebels on Thursday leveled a historic hotel being used as an army base in the northern city of Aleppo by detonating bomb-packed tunnels beneath it, activists and militants said.

The blast near Aleppo's medieval citadel, an imposing city landmark that was once swarming with tourists, killed an unknown number of soldiers. It turned the Carlton Hotel, known for its elegant architecture and proximity to the citadel, into a pile of rubble.

The attack was a powerful statement that the rebels could still deal heavy blows elsewhere in Syria even as they withdrew from Homs, surrendering that city to President Bashar al-Assad's forces.

In Homs, 95 miles south of Aleppo, army troops were poised to enter the city's old quarters after hundreds of fighters complete their evacuation, which was suspended after gunmen in northern Syria prevented trucks carrying aid from entering two villages besieged by rebels. The aid delivery was part of the cease-fire agreement allowing rebels to leave Homs.

Earlier, footage from Homs broadcast by the pro-Syrian Al-Manar TV showed rebels, many of them covering their faces and carrying backpacks, boarding a bus, its windows covered with newspapers.

An Associated Press journalist in Homs on Thursday reported massive destruction. Standing near the city's main square, the streets appeared almost apocalyptic. Even the trees were burnt.

The withdrawal from Homs, in line with a cease-fire agreement reached last week, is a major win for Assad. But Thursday's explosion in Aleppo was a reminder that rebels, although weakened in the country's center and west, remain a force elsewhere.

The Britain-based Syrian Observatory for Human Rights, which has a network of activists on the ground, said at least 14 soldiers were killed. The Islamic Front, Syria's biggest rebel alliance which claimed the attack, said 50 soldiers died. The claims could not be independently verified.