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 bombs in tunnels dug 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. And 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 withdraw from Homs, the nation’s third-largest city, which they have surrendered to President Bashar Assad’s forces.
Those government forces, meanwhile, were poised Thursday to enter Homs’s old quarters when the rebels’ evacuation is complete. The evacuation was suspended Thursday after gunmen in northern Syria prevented trucks carrying aid from entering two villages besieged by rebels. The aid delivery was part of a cease-fire agreement that allowed rebels to leave Homs for rebel-held areas farther north.
Earlier, footage from Homs broadcast by the pro-Syrian Al-Manar TV showed rebels, many of them covering their faces with masks and carrying backpacks, boarding a green bus, its windows covered with newspapers.
An Associated Press journalist who visited Homs on Thursday reported massive destruction, the streets surrounding the city’s main square appearing almost apocalyptic. Even the trees were burnt.
Buildings along Dablan Street were completely shattered with gaping holes, crumbled facades, and flattened upper floors, testimony to what Homs has endured in more than two years of fighting. A cafe was scorched. Rubbish, glass, debris, fallen trees, and electricity poles blocked deserted roads that intersected with Dablan Street.
A police officer wearing a uniform with a picture of an eagle and the words ‘‘Syria’s Assad’’ patrolled a nearby street.
‘‘Words cannot describe what has happened here,’’ said Abdel Nasser Harfoush, a 58-year-old Homs resident who lost his business. He said he hoped the agreement will end the bloodshed and restore peace and stability to the city.
The rebels’ withdrawal is a major win for Assad. Militarily, it solidifies the government’s hold on a swath of territory in central Syria, linking the capital Damascus with government strongholds along the coast and giving a staging ground to advance against rebel territory farther north.
Politically, gains on the ground boost Assad’s hold on power as he seeks to add a further claim of legitimacy to the June 3 presidential elections, which Western powers and the opposition have dismissed as a sham.
But Thursday’s massive explosion in Aleppo was a powerful reminder that rebels — although weakened in the country’s center and west — are still a potent force elsewhere, particularly in the north.
The Britain-based Syrian Observatory for Human Rights, which maintains a network of activists on the ground, said at least 14 soldiers were killed in the blast. The Islamic Front, Syria’s biggest rebel alliance, which claimed responsibility for the attack, said 50 soldiers died.
Neither group indicated how it determined the death toll, and the claims could not be independently verified.
In a live broadcast from the site of explosion, Syrian TV’s correspondent in Aleppo said that the army had been using the building as a base, and that soldiers were positioned there at the time of the blast. The correspondent did not mention casualties but said the rebels blew up the building by tunneling underneath and planting explosives.
‘‘They use tunnels like rats, because they cannot face the Syrian Arab Army,’’ the correspondent said, adding that the explosion felt like an earthquake to those around Aleppo.
The Syrian government does not publicize its casualties in the civil war.
Aleppo has been carved up into opposition- and government-held areas since the rebels launched an offensive there in mid-2012, capturing territory along Syria’s northern border with Turkey.