At least 50 people were Sunday killed across Syria, where opposition activists said President Bashar al-Assad's troops had stepped up attacks on pro-rebel areas. The bulk of the deaths occurred in restive areas near the capital Damascus and the northern city of Aleppo, said the opposition Syrian Observatory for Human Rights.
Sounds of exploding shells and machine gun fire could be heard across Damascus, as fighting between government troops and rebels raged in the north-eastern suburb of Harasta, added the London-based organisation.
The watchdog said helicopter gunships had pounded the opposition bastions of Hanano and Sakhur in the north of Aleppo and the district of Bustan al-Qasr in the south-western part of the embattled city.
Rebels meanwhile claimed they had regained "full control" of the neighbourhood of Salaheddin in the south of Aleppo from al-Assad's troops. Both sides have been fighting in Aleppo, Syria's biggest city and commercial hub, for more than two months.
Syrian troops shelled the restive town of al-Rastan in the central province of Homs, said the observatory. The violence coincided with the presence of United Nations-Arab League envoy Lakhdar Brahimi in Damascus, where he met al-Assad on Saturday and warned that the conflict in Syria posed a global threat.
Brahimi Sunday met with more Syrian opposition figures who are tolerated by the regime and also with government officials, said a Syrian source.
He was due to leave Damascus later in the day ending a four-day visit. Brahimi has said that he has no specific plan at this point for ending the 18-month conflict, which the opposition said had claimed more than 27,000 lives. The UN puts the figure at 20,000.
Brahimi, a veteran Algerian diplomat, said "a plan will be set after listening to all internal, regional and international parties," and said he hoped that such a plan would help set the scene for resolving the crisis.
In neighbouring Lebanon, local broadcasters reported that Syrian forces had pushed some 200 meters inside Lebanese territory and blew up two farms in the eastern Bekaa Valley, allegedly in chase of rebels.
The incident did not cause injuries, but prompted the Lebanese army to deploy troops to the area to head off the recurrence of such attacks.
The Syrian government has repeatedly accused Lebanese factions loyal to former Sunni-Muslim premier Saad Hariri of assisting the Syrian opposition.