Fighting in Syria has continued with government forces buoyed by a recent victory in Qusayr, and ahead of a G8 summit where leaders are expected to discuss a coordinated response to the conflict.
There was heavy shelling in Ghouta on Sunday on the eastern outskirts of the Syrian capital, with activists' videos showing intense fighting in Al Rastan in Homs, as the Syrian army bombed the Al Asali district in Damasus.
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The violence came a day after Mohamed Morsi, the Egyptian president, announced that Cairo was cutting off diplomatic relations with Syria and ordered that the Damascus embassy in Cairo to be closed.
"The situation in Syria is absolutely critical right now," said Al Jazeera's Andrew Simmons, who has recently returned from reporting in Aleppo. "Morale is low amont the rebels [after losing Qusayr]."
As tension escalates, rebel fighters and government forces have both adopted stricter strategies and, for instance, are no longer trading prisoners for money, Simmons said.
Adding in Egypt's move, and with the US and Russia remaining at odds on how to help solve the conflict, there is also "a diplomatic escalation," too, Simmons said.
Meanwhile, British Prime Minister David Cameron will hold talks on Sunday with Russian President Vladimir Putin on Syria's civil war, a meeting which could set the tone for the G8 summit, with the West at odds with Moscow over how to handle the conflict.
Cameron is seeking to forge a consensus as he hosts the leaders of the world's top industrialised nations in Lough Erne, Northern Ireland, from Monday.
Washington has upped the ante on Syria by vowing to send military aid to rebel forces battling to topple President Bashar al-Assad after saying it had proof that the regime had crossed a "red line" by using chemical weapons on a small scale.
Ahead of his talks at Downing Street with Putin, Cameron said it was essential to assist the moderate rebels prepared to work with the West before fighters linked to al-Qaeda gained the upper hand in the opposition.
"I want to help the Syrian opposition to succeed and my argument is this: yes, there are elements of the Syrian opposition that are deeply unsavoury, that are very dangerous, very extremist, and I want nothing to do with them," he told Sky News television.
"But there are elements of the Syrian opposition who want to see a free, democratic, pluralistic Syria that respects the rights of minorities, including Christians, and we should be working with them."
On Saturday, Morsi told thousands of supporters in a rally that his government is withdrawing the Egyptian charge d'affaires from Damascus.
He also called on Lebanon's Hezbollah armed group to leave Syria, where the Shia movement has been fighting alongside troops loyal to the embattled president against the rebel forces.
"We stand against Hezbollah in its aggression against the Syrian people," Morsi said. "Hezbollah must leave Syria - these are serious words. There is no space or place for Hezbollah in Syria."
Morsi also said the international community should implement a no-fly zone over Syria - which the US is considering.