Rebels level historic Aleppo hotel in Syria

HOMS, Syria -- With a gigantic explosion, Syrian rebels 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, a city landmark once swarming with tourists, killed an unknown number of soldiers. It turned the Carlton Hotel, known for its architecture and proximity to the citadel, into a pile of rubble.

The attack was a statement that the rebels could still deal heavy blows elsewhere in Syria even as they withdrew from Homs, surrendering that city to President Bashar 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 finish 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 allowing 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. Near the city's main square, known as Clock Square, the streets appeared almost apocalyptic. Even the trees were burned.

Buildings along Dablan street were shattered with gaping holes, crumbled facades and flattened upper floors, testimony to what Syria's third-largest city has endured in more than two years of fighting. A popular cafe and restaurant was scorched. Rubbish, glass, debris, fallen trees and electrical poles blocked deserted roads that intersected with Dablan street.

A policeman 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 his city.

The withdrawal, in line with a cease-fire agreement reached last week following a fierce, two-year battle, 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 in 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 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 blast, Syrian TV's correspondent in Aleppo stood on a huge pile of rubble with twisted metal and palm trees sticking out, saying that the army had been using the building as a base and soldiers were positioned there at the time of the explosion. In the broadcast, the station 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. The bombing took place in a contested area where rebel and government territory almost crisscross.

An Aleppo-based member of the Islamic Front's media office, who goes by the name of Hussein Nasser, said the rebels spent days digging the nearly 100-meter (yard) deep tunnel under the hotel and filled it with locally made bombs.

He added that the explosives, made up of chemical fertilizers, weighed about 20 tons.

"Today's explosion was as powerful as two barrel bombs that the regime uses," he said referring to the crude bombs used by government air strikes that usually knock down a building.

In recent months, government aircraft have relentlessly bombed rebel-held parts of the city. Opposition fighters have hit back, firing mortars shells into government-held areas. The rebels also have detonated car bombs in residential neighborhoods, killing dozens of people.

Thursday's attack was the second carried out by the Islamic Front against the Carlton. The first, allegedly also involving explosives-packed tunnels, caused a partial collapse of the building in February. The Front, an alliance of several Islamic groups fighting to topple Assad, appears to favor this technique and has used it in deadly attacks against government forces in Aleppo and Idlib provinces.

The latest bombing was much more powerful than the February attack and sent an enormous mushroom of gray smoke into the sky and over the ancient city, according to a video posted online by activists. The video appeared genuine, matching AP's reporting on the blast.

Also Thursday, the head of the mission charged with destroying Syria's chemical weapons said the last 16 containers of chemical agents awaiting transport out of the country are in a contested area near Damascus that is currently inaccessible.

Sigrid Kaag told reporters after briefing the U.N. Security Council that it's not possible to arrange a cease-fire so authorities can get to the site where five containers of the most dangerous chemicals and 11 containers of less toxic chemicals -- representing 8 percent of Syria's declared stockpile -- are awaiting removal. Syria missed an April 27 deadline for all chemical agents to be removed or destroyed in the country.

Stepping up pressure on Syria, the U.S. Treasury Department sanctioned six Syrian officials and a Russian bank for their alleged support of Assad's government. To date, the United States has imposed sanctions on nearly 200 individuals and entities, including the government of Syria, its central bank, and affiliated oil companies.

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Karam reported from Beirut. Associated Press writers Bassem Mroue, Barbara Surk and Yasmine Saker in Beirut, and Deb Riechmann in Washington, contributed to this report.