France has signalled that it is prepared to take part in enforcing a partial no-fly zone over Syria, piling pressure on President Bashar al-Assad's embattled regime as it widens a major offensive against rebels in Damascus and surrounding areas.   

French Defence Minister Jean-Yves Le Drian urged the international community Thursday to consider backing a no-fly zone over parts of Syria, but cautioned that closing the Arab nation's entire air space would be tantamount to "going to war" and require a willing international coalition that does not yet exist.   

He told France 24 television that Paris would participate in a full no-fly operation if it followed international legal principles. But for now, he suggested that a partial closure — which U.S. Secretary of State Hillary Clinton said Washington was considering — should be studied.   

Civil war rages   

In Syria, troops backed by tanks and helicopters broke into the Damascus suburb of Daraya, the scene of intense fighting over the last two days. At least 18 people were killed.

Across the country, at least 100 people died Thursday in shelling and clashes, according to the Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees.

The bloodshed coincided with the departure from the Syrian capital of the last of the United Nations military observers after their mission failed. The observers were part of a six-point peace plan by outgoing envoy Kofi Annan.   

As the country slides deeper into civil war, activist groups now routinely report the deaths of anywhere between 100 and 250 people on a daily basis, but it is virtually impossible to verify these figures.

Residents of Damascus said troops were bombing Daraya and nearby Moadamiyeh from the Qasioun mountain overlooking Damascus.

"It's just another regular day in Damascus," said a resident of the city of 1.7 million, who spoke on condition of anonymity for fear of reprisals. "I woke up to the sound of explosions and it hasn't stopped since."

Battle in al-Bukamal

In the eastern part of the country, Syrian rebels fought with regime troops in the town of al-Bukamal, across the border from the Iraqi town of Qaim.

The border crossing has been in rebel hands since last month, but wresting control of al-Bukamal itself from regime troops would expand the opposition foothold along the frontier.   

The opposition already controls a wide swath of territory along the border with Turkey in the north, as well as pockets along the frontier with Jordan to the south and Lebanon to the west. Together, they have proven key to ferrying people and supplies into and out of the country.

Rebels have been fighting troops for days in al-Bukamal and early Thursday took over several checkpoints, the main police station and the local command of the Political Security Directorate, one of Syria's powerful intelligence agencies, according to Rami Abdul-Rahman, who heads the Observatory.

"There is an attempt to take full control of al-Bukamal," Abdul-Rahman said.

The Local Coordination Committees said warplanes bombed al-Bukamal, but Abdul-Rahman said the jets were flying over the town and struck nearby areas, not the town itself.

At least six people were killed, activists said.   

The seemingly intractable conflict in Syria has defied all attempts at mediation. Human rights groups say more than 20,000 people have been killed since the uprising against Assad began in March 2011. In the past month the fighting has spread from the country's smaller towns and cities to the regime strongholds of Damascus and Aleppo.

Chemical weapons under control, Russia says

The potential use of chemical weapons in the Syrian conflict has put Russia in a rare point of agreement with the United States, which has pressured Assad to step down.   

Syria first acknowledged its possession of chemical weapons last month and threatened to use them if foreign nations intervened militarily in the conflict.   

U.S.President Barack Obama said Monday the United States might have to intervene in Syria if the Assad regime used or moved chemical weapons. He also warned of the threat of such weapons falling into the hands of rebels fighting the government or militant groups aiding either side.   

Deputy Foreign Minister Gennady Gatilov, Russia's point man on Syria, said his country was in full agreement with the Americans on the need to prevent Assad's regime from using the weapons or allowing them to slip out from under its control. 

"We have guarantees from the Syrian government that it will not take any steps involving chemical weapons," Gatilov told The Associated Press.   

Senior diplomatic, military and intelligence officials from the U.S. and Turkey met in Istanbul on Thursday to go over detailed operational plans for dealing with emergency scenarios that may arise in Syria, including the possible use of chemical weapons.   

These include positioning stocks of bio-hazard gear in the region as part of the planning for an international response if chemical weapons are used, U.S. officials said.