Jihadists have seized a strategic army base in northern Syria, a watchdog said, as the EU piled more pressure on President Bashar al-Assad by edging closer to a newly formed opposition bloc.
The Syrian Observatory for Human Rights also reported clashes in a northern Damascus district, the fiercest in the area since a revolt against Assad's regime erupted in March 2011.
The European Union gave a vital boost to members of the National Coalition, describing them as the "legitimate representatives of the Syrian people" following talks in Brussels with the bloc's leader, Ahmed Moaz al-Khatib.
The EU, winner of this year's Nobel Peace Prize, said at the award ceremony in Oslo that the 21-month conflict in Syria, which has cost more than 42,000 lives, must be addressed.
"Let me say it from here today. The current situation in Syria is a stain on the world's conscience and the international community has a moral duty to address it," said European Commission president Jose Manuel Barroso.
The Independent newspaper said Tuesday Britain and other key international players were actively drawing up plans to train rebel fighters and back them with air and naval support.
General David Richards, the head of Britain's armed forces, held talks recently in London with military leaders from France, Turkey, Jordan, Qatar, the UAE, and a US general, according to a report on the newspaper's website.
During the meeting organised at the request of Prime Minister David Cameron, the military chiefs are believed to have held detailed strategic discussions about how to help rebels.
Britain, France and the United States have pledged not to put "boots on the ground" to help the rebels, meaning Turkey would most likely host the training camps.
Britain's Ministry of Defence would not confirm the report.
"We want to see a diplomatic solution to the crisis in Syria that leads to an end to the violence and a process of genuine political transition," said an MoD spokesperson.
"In the absence of a political and diplomatic solution, we will not rule out any option in accordance with international law that might save innocent lives in Syria."
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The capture by the Al-Nusra Front and allied jihadist groups of the base at Sheikh Suleiman dealt a significant blow to Assad's regime as it had been the last major military base west of Aleppo city still under army control.
But it also undercut the military influence of the mainstream rebel Free Syrian Army (FSA).
An AFP journalist who covered the clashes around Sheikh Suleiman said many fighters were from other Arab countries and Central Asia.
"We control the whole base, all the zone is under our control. The whole region west of Aleppo up to the Turkish border has now been liberated. But no chemical weapons were found, or anti-aircraft missiles," said a rebel chief, Abu Jalal.
He headed the only unit of the mainstream rebel FSA which took part in the operation.
Also on Monday, the army used warplanes and tanks to bombard rebel positions in Damascus province and violent clashes broke out in the north of the capital, the Observatory said.
Violence in Damascus has previously been focused on southern districts.
At least 94 people, among them 42 civilians, 26 soldiers and 26 rebels, were killed in nationwide violence on Monday, said the Observatory, which relies on activists and medics for its information.
The highest toll was in Damascus province, where 36 people died.
Arab and Western states will consider two key issues at a Friends of Syria meeting in Marrakesh on Wednesday -- the political transition in the event of Assad's fall, and mobilising vital humanitarian aid as winter sets in.
US Secretary of State Hillary Clinton had been due to attend, but has cancelled her planned trip to Morocco because of a stomach virus, her office said.
And as concerns mount in the West that hardline Islamists are hijacking the uprising, Washington is set to declare the Al-Nusra Front a "foreign terrorist organisation," according to documents posted in the US Federal Register.