Fighting rages in Syria as UN ends mission

Fighting is raging in Syria's key cities, a day after the United Nations formally ended its observer mission in the war-torn country, opposition sources say.

The United Nations is to let its military observer mission's mandate in Syria expire.

Sounds of explosions on Friday in the capital Damascus were followed by clashes near a military airport, said activist Haytaham al-Abdallah.

Fierce fighting also continued in Aleppo, Syria's biggest city, for a third consecutive week.

"The intensity of the shelling by the regime in Aleppo has increased in the past 24 hours,"

Abu Omar al-Halabi, a commander in the rebel Free Syrian Army commander, said.

"The regime troops are using high-calibre shells that can bring down a building of six floors in one shell," he told DPA by phone from Aleppo.

The battle for Aleppo, Syria's commercial hub, could decide the course of the 18-month conflict.

At least seven people were killed by government forces in the town of al-Quseir, in the dissident province of Homs in central Syria, reported activists.

Around 250 people were killed across Syria on Thursday, reported the Syrian Observatory for Human Rights, a London-based opposition group.

The surge in violence came just hours after the UN Security Council decided not to extend the mandate of its observer mission in Syria.

The observers were dispatched to Syria in April to monitor a ceasefire, which never held.

In Lebanon, meanwhile, the powerful Shi'ite al-Mokdad clan released 18 of the 40 Syrians it had kidnapped on Wednesday in a bid to secure the release of one of its relatives held by rebels in Syria.

"At this moment, we have halted all operations on Lebanese territory ... because we have a sufficient number of Syrians linked to the (rebel) Free Syrian Army," said Maher al-Mokdad, a member of the clan.

The kidnappings have raised concerns that the Syrian conflict is spilling over the border into Lebanon, which, like Syria, is divided along sectarian lines.