This image taken from video obtained from the Shaam News Network, which has been authenticated based on its contents and other AP reporting, shows heavy shelling by warplanes in the Eastern Ghouta area near Damascus, Syria, Monday Dec. 10, 2012. (AP Photo/Shaam News Network via AP video)

Darrett Ezza, Syria -

Jihadists led by the radical Al-Nusra Front seized a strategic army base in the northern Syrian province of Aleppo on Monday, in a fresh setback for President Bashar al-Assad's regime, a watchdog said.

The Syrian Observatory for Human Rights also reported clashes in a northern Damascus district, the fiercest in the area since a revolt against Assad broke out in March 2001.

Also on Monday, ahead of a “Friends of Syria” meeting in Morocco later this week, EU foreign ministers met the head of the newly formed Syrian opposition coalition.

And the European Union, winner of this year's Nobel Peace Prize, said at the award ceremony in Oslo that the 21-month conflict in Syria that has cost tens of thousands of lives was “a stain” on the world's conscience.

“Let me say it from here today,” said European Commission president Jose Manuel Barroso. “The current situation in Syria is a stain on the world's conscience and the international community has a moral duty to address it.”

The statement came as EU foreign ministers welcomed Ahmed Moaz al-Khatib, head of the newly formed National Coalition, as “a clear signal of how the status of the Syrian coalition is being reviewed,” German Foreign Minister Guido Westerwelle said.

“It is a coalition which represents the legitimate interests of the Syrian people. We want that to be recognised as such by the European Union,” Westerwelle said.

The EU currently recognises the coalition as “legitimate representatives of the aspirations of the Syrian people,” which falls short of recognising it outright as a potential future government.

Germany, for its part, on Monday expelled four employees of the Syrian embassy in Berlin, as part of moves to further isolate Assad's regime.

“We are sending a clear message with the expulsion of four Syrian embassy staff that we are reducing relations with the Assad regime to an absolute minimum,” Westerwelle said.

Inside Syria, the capture by Al-Nusra Front and allied jihadist groups of the base at Sheikh Suleiman dealt a blow to Assad's regime in the region 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 of the fighters were from other Arab countries and Central Asia.

A rebel chief told AFP that no chemical weapons or surface-to-air missiles were found on the base.

“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 Abu Jalal.

The rebel chief headed the only unit of the mainstream rebel FSA which took part in the operation.

Elsewhere, as the army used warplanes and tanks to bombard rebel positions in Damascus province, violent clashes broke out in the northern Damascus district of Sheikh Mohieddin.

Violence in Damascus has previously been focused on southern districts.

At least 51 people, among them 13 civilians, 26 soldiers and 12 rebel fighters, were killed in violence across Syria on Monday, said the Observatory, which relies on activists and medics for its information.

The latest violence came two days ahead of a Friends of Syria nations meeting in Marrakesh, bringing together countries which support the anti-Assad revolt.

Arab and Western states will consider two key issues concerning the conflict Ä the political transition in the event of Assad's fall, and mobilising vital humanitarian aid as winter sets in.

Since the last meeting, in Paris in July, the number of people killed has risen from 16,000 to more than 42,000, according to the Observatory.

Continued violence prompted Syrian human rights lawyer Anwar al-Bunni to call on the the international community on Monday to “dedicate” World Human Rights Day this year to the Syrian people.

Efforts should be made “to allow this people to have its rights, just like people all over the civilised world,” Bunni said, citing “terrible violations” of human rights in war-ravaged Syria. - Sapa-AFP