Turkey seals border with Syria as fighting rages; Assad regime hit with new diplomatic defections

Free Syrian Army fighters stand near a fallen Syrian flag at the Bab al-Salam border crossing to Turkey, July 22, 2012.

(CBS/AP) BEIRUT - Turkey sealed its border with Syria to trucks on Wednesday, cutting off a vital supply line to the embattled nation as fighting stretched into its fifth day in the commercial capital of Aleppo.

Turkish Economy Minister Zafer Caglayan said deteriorating security was behind the closure.

"We have serious concerns over the safety of Turkish trucks regarding their entry and return from Syria," Caglayan said, noting that there had already been a 87 percent drop in trucks traveling to Syria this year.

Turkey was an ally of neighboring Syria before the uprising against authoritarian President Bashar Assad began 16 months ago. But it has turned into a harsh critic and its territory along the of the 566-mile border is used as a staging ground for the rebel army as well as a haven for thousands of refugees fleeing violence that activists say has killed 19,000 people so far.

In a fresh blow to the autocratic regime of President Bashar Assad, meanwhile, another senior diplomat announced his defection on Wednesday. The Syrian Ambassador to the United Arab Emirates, Abdel Latif al-Dabbagh, announced his defection from the regime, just one a day after the Syrian envoy to Cyprus did the same.

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Northern Syria, especially the province of Idlib, has been a steady scene of heavy fighting between Syrian forces and the rebels and large swathes of the countryside are under rebel control. Rebels, for their part, generally move their weapons and material over the border through clandestine smuggler routes.

Caglayan told reporters Turkish trucks would not be allowed to into Syria, though no restrictions were being imposed on trucks going the other way. The sealing will deprive Syria of a common route for imports. Dozens of Turkish trucks were either looted or torched when the rebels captured the border crossing of Bab al-Hawa last week. Turkish truck drivers have also been caught in the cross fire or been the target of attacks during the civil war.

In Washington, U.S. Secretary of State Hillary Rodham Clinton expressed confidence at rebel advances, saying that they were taking more and more territory.

"It will eventually result in a safe haven inside Syria, which will then provide a base for further actions by the opposition," she said Tuesday, urging the opposition to develop institutions and protect the rights of all Syrians.

The ability of the Libyan rebels to create a liberated area in the east of the country was key in their successful battle that ousted Muammar Qaddafi last year. However Syrian rebels' hold over territory is tenuous. They do not have any major urban areas under their control — and are not backed by NATO's air force the way the Libyans were.

The U.S. government's verbal support for the rebels drew fresh criticism from Russia on Wednesday, with the Kremlin's top diplomat blasting earlier remarks from a State Department spokeswoman as "a direct justification of terrorism."

Foreign Minister Sergey Lavrov was referring to a comment by State Department spokeswoman Victoria Nuland, who said a Damascus bomb attack claimed by the rebels - which killed four top members of the Assad regime - was not surprising, given the government's harsh tactics against opposition supporters.

The main battle in Syria is currently just 40 miles from the Turkish border in the commercial hub of Aleppo, Syria's largest city, which was attacked on Saturday by an alliance of rebel forces. They infiltrated sympathetic neighborhoods in the north and south and then have been gradually moving toward the historic old city at the center, a U.N. world heritage site.