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UN: 200,000 civilians flee fierce fighting in Syria commercial hub

For days the Syrian troops' weapons have given them the upper hand during key battles in Aleppo, but the rebels – now armed with powerful shoulder fired anti-aircraft missiles -- are preparing for a different kind of fight. NBC's Richard Engel reports.

Updated at 11:32 a.m. ET: Fierce battles between government forces and opposition fighters in Syria’s commercial hub Aleppo have forced an estimated 200,000 civilians to flee the city, according to aid groups.

U.N. Under-Secretary General for Humanitarian Affairs and Emergency Relief Coordinator Valerie Amos, citing reports from the International Committee of the Red Cross and the Syrian Arab Red Crescent, said Sunday that she was "extremely concerned by the impact of shelling and use of tanks and other heavy weapons on people in Aleppo."

In what is seen as a huge blow to Syria's President Assad, his most senior diplomat in the U.K. quit his post. Khaled al-Ayoubi, the Syrian charge d'affaires in London, told British authorities he was "no longer willing" to represent his government, because of its "violent and oppressive actions." ITV's Chris Ship reports.

"Life in Aleppo has become unbearable. I'm in my car and I'm leaving right now," a Syrian writer told The Associated Press as he got ready to drive away. "There's shelling night and day, every day," he said over the telephone on condition of anonymity for fear of reprisals.

He painted a dire picture of daily life in the embattled city, torn between the government forces and those of the rebels.

"Bread, gasoline and gas are being sold on the black market at very high prices," he said. "Many things are in shortage."

The past two weeks have seen forces of President Bashar Assad struggle to maintain their grip on the country after a major rebel advance into the two main cities, Aleppo and Damascus, and a July 18 explosion that killed four top security officials.

Rebel fighters and government forces are still fighting in Syria's commercial hub of Aleppo. NBC's Richard Engel reports.

Government forces have succeeded in imposing their grip on Damascus but rebel fighters gained control of parts of Aleppo, a city of 2.5 million people, where journalists have toured neighborhoods dotted with Free Syrian Army checkpoints flying black and white Islamist banners.

Since the rebel assault on Aleppo began a week ago, about 192 people have been killed, mostly civilians, according to the activist group Syrian Observatory for Human Rights. Some 19,000 people have died since the uprising began, the group says.

The battle for Aleppo, once a bastion of support for Assad's regime, is critical in the struggle for Syria's future. Rebels already control large sections of the neighboring Idlib province, which borders Turkey, and if a major metropolis fell to them it could possibly create the nucleus of some kind of "liberated" territory that could receive further support from the international community — much the way eastern Libya became a rebel sanctuary during the fight against Moammar Gadhafi last year.

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Yet Syria's rebels are still massively outgunned and it seems just a matter of time before Assad's massed forces outside the city crush them, much the way a similar rebel assault on Damascus over a week ago was quashed.

Civilians in need
Amos, of the United Nations, said the violence in the Aleppo region made it difficult for aid agencies to reach civilians in need.

Rebels in Aleppo shoot at Syrian government helicopters during an intense battle on Saturday.

"Many people have sought temporary shelter in schools and other public buildings in safer areas. They urgently need food, mattresses and blankets, hygiene supplies and drinking water," she said in a statement.

"I call on all parties to the fighting to ensure that they do not target civilians and that they allow humanitarian organizations safe access to bring urgent and life-saving help to people caught up in the fighting," Amos added.

U.S. Defense Secretary Leon Panetta said attacks on Aleppo showed Assad lacked the legitimacy to rule.

"If they continue this kind of tragic attack on their own people in Aleppo, I think it ultimately will be a nail in Assad's own coffin," Panetta said, speaking to reporters at the start of a weeklong trip to the Middle East and North Africa.

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"What Assad has been doing to his own people and what he continues to do to his own people makes clear that his regime is coming to an end," he said, adding, "It's no longer a question of whether he's coming to an end, it's when."

Scenes of destruction in Aleppo
Fighting for the past several days has focused on the Salaheddine district in the southwest of Aleppo, where government troops have been backed by helicopter gunships.

Rebel fighters, patrolling opposition districts in flat-bed trucks flying green-white-and-black "independence" flags, said they were holding off Assad's forces in Salaheddine. However, the government said it had pushed them out.

"Complete control of Salaheddine has been (won back) from those mercenary gunmen," an unidentified military officer told Syrian state television late Sunday. "In a few days safety and security will return to the city of Aleppo."

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Reuters journalists in the city were not able to approach the district after nightfall on Sunday to verify whether rebels had been pushed out. The Syrian Observatory for Human rights said fighting was continuing there.

The government also declared victory Sunday in the battle for the capital, which the rebels assaulted in force two weeks ago but have been repulsed in unprecedented fighting.

Cars entering one Aleppo district came under fire from snipers and a Reuters photographer saw three bodies lying in the street. Unable to move them to hospital for fear of shelling, residents had placed frozen water bottles on two of the corpses to slow their decomposition in the baking heat.

A burned-out tank lay in the street, while nearby another one had been captured intact and covered in tarpaulin. Burned cars could be seen in many streets, some marked with "shabbiha" - a reference to pro-Assad militiamen.

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Near the center of town, most shops were shuttered, some with "Strike" painted over them. The only shop doing business was a bakery selling subsidized bread, where the line stretched around the block.

With the Assad regime directing the full force of its military at Aleppo, Syria's biggest city, the Syrian government is pulling forces out of surrounding towns -- a cause for celebration among rebels there. NBC's Richard Engel reports from inside one of those towns, in northern Syria.

Syria's top diplomat in Britain defects
In London, the British Foreign Office said Monday that Syria's most senior diplomat in the country had defected.

Khaled al-Ayoubi, the embassy's charge d'affaires, told officials that he was not willing to represent Assad's regime any longer.

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"Mr. al-Ayoubi has told us that he is no longer willing to represent a regime that has committed such violent and oppressive acts against its own people," the Foreign Office said. "We urge others around Bashar Al-Assad to follow Mr. al-Ayoubi's example; to disassociate themselves from the crimes being committed against the Syrian people and to support a peaceful and free future for Syria."

Al-Ayoubi's departure represents the latest in a series of diplomatic and other defections from Assad's regime.

Reuters and The Associated Press contributed to this report.

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