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

French Defense Minister Jean-Yves Le Drian urged the international community 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.

Syria's chief backer, Russia, meanwhile, said it was working closely with the Damascus government to ensure that its arsenal of chemical weapons stays under firm control and has won promises that it will not be used or moved.

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."

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.

Meanwhile, the Washington Post reported that an American freelance journalist who has been reporting from Syria for The Post, McClatchy Newspapers and other outlets had not been heard from in more than a week. Austin Tice, 31, spent time with rebel fighters in the north after entering Syria from Turkey in May, then traveled to Damascus, where he was one of the few Western journalists reporting from the capital.

"We're focused intensively on trying to ascertain his whereabouts and ensure his safe return," Post executive editor Marcus Brauchli said in a statement.

Spokeswoman Victoria Nuland said the U.S. State Department was working through the Czech Embassy, which represents U.S. interests in Syria, to get more information about Tice's welfare and whereabouts.

"We have long expressed concern about the safety for journalists in Syria, and note that freedom of movement throughout the country for journalists is one of the 6 points in the Annan Plan endorsed by the United Nations Security Council," she said in a statement. " We strongly urge all sides to ensure the safety of journalists in Syria."

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.

Annan announced earlier this month that he will resign on Aug. 31. He is to be replaced by veteran diplomat Lakhdar Brahimi.

In Damascus, Deputy Foreign Minister Faysal Mekdad said Syrian officials were "looking forward" to working with Brahimi but said the crisis would continue as long as foreign countries were interfering.

Mekdad accused Turkey of giving "terrorists," including al-Qaida, free access to cross into Syria from Turkey. The Syrian regime refers to the rebels as terrorists.

Turkey — once an ally of Syria — has emerged as one of Assad's harshest critics and taken in some 44,000 refugees from its Arab neighbor.

The main battle fronts over the past month have been in the capital, Damascus, as well as Aleppo, where regime forces have struggled to stamp out a rebel offensive that began last month and succeeded in capturing several districts in the city of 3 million people.

In a report released Thursday, Amnesty International said artillery, mortar fire and airstrikes by government forces in Aleppo are killing mostly civilians, including children.

The rights group said that during a 10-day, fact-finding visit to Aleppo in the first half of August, it found that some 30 attacks killed more than 80 civilians and wounded many more.

Amnesty said that among the dead were 10 members of one family, seven of them children, whose home was destroyed in two airstrikes on Aug. 6. It said the bodies of young men, many of them handcuffed and shot in the head, were found near the local headquarters of the powerful Air Force Intelligence, which is in a government-controlled area.

The uprising against Assad's regime began with largely peaceful protests but has since morphed into a civil war that has spread to almost all parts of the country.

In Daraya, the Local Coordination Committees said the government shelling killed a mother and her five children, all members of the al-Sheik family who had fled their hometown of Moadamiyeh to escape the violence. An amateur video showed the children draped in white shrouds with their faces showing; the body of the mother was covered.

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.

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.


AP reporters Sarah DiLorenzo in Paris, Lynn Berry in Moscow, Albert Aji in Damascus and Matthew Lee in Washington contributed to this report.