BEIRUT -- Syrian fighter jets on Sunday bombed Damascus suburbs in a government offensive to dislodge rebels from strategic areas around the capital, activists said, as clashes raged around army bases and airfields in the country's north.

The Britain-based Syrian Observatory for Human Rights said warplanes were hitting towns and villages around the capital, including Kfar Batna and Gesereen, while regime forces targeted other neighbourhoods with artillery and mortars. At least nine people were killed when a shell hit eastern Ghouta district, the group said.

Also Sunday, Turkish state media said Assad's fighter jets bombed the Syrian town of Azaz near the Turkish border.

At least 34 Syrians wounded in the airstrikes were brought across the border to the Turkish province of Kilis for treatment, the state-run Anadolu agency said. Seven died of the injuries, the report said.

The Observatory said troops were battling rebels in the suburb of Daraya a day after government officials claimed the army had taken much of the strategic area, which lies on the edge of a major military air base southwest of the capital.

In northern Syria, government forces were fighting rebels over an air base and the international airport of the city of Aleppo. The airport includes a military base.

Syrian troops have been pushing since November to regain Daraya, which had a population of about 200,000 before the fighting. Thousands have fled the relentless violence, among more than 2 million Syrians who have been internally displaced during the civil war. At least half a million Syrians have fled to neighbouring countries like Turkey, Lebanon and Jordan.

Observatory director Rami Abdul-Rahman said government troops now control more than half the suburb, a stronghold of support for the rebels since the start of the uprising against President Bashar Assad in March 2011.

Because of its strategic location, rebel control of the Daraya poses a particularly grave threat to the capital.

The suburb is flanked by the key districts of Mazzeh, home to a military air base, and Kfar Sousseh, where the government headquarters, the General Security intelligence agency head office and the Interior Ministry are located. It also is less than 10 kilometres (six miles) from a presidential palace.

While Assad's loyalists appear to have an upper hand on the Damascus front due to the regime's air power, the rebels dealt the government a major blow in the north by capturing a sprawling air base in Idlib province on Friday.

Rebels retained control of the Taftanaz base Sunday and intensified their assault on the Mannagh air base and the international airport in Aleppo, Syria's largest city, activists said.

Among the rebels taking part in the battle are fighters from Jabhat al-Nustra, an Islamist group that the U.S. has branded a terrorist organization. Washington said the group, among the most organized and effective rebel forces on the ground, is affiliated with al-Qaida.

Syrian official statements regularly play up the role of Islamist militants in the civil war and refer to the rebels as terrorists.

More than 60,000 people have been killed since the revolt started almost two years ago.

Heavy fighting was reported Sunday in the northern province of Deir el-Zour, involving attacks by warplanes, activists said. Clashes between rebels and troops were concentrated on the area around the airport outside the city of Deir el-Zour that has been under siege by the government forces for weeks.

Last month an international aid group, Doctors Without Borders, said tens of thousands of Syrians, many of them wounded, are trapped in Deir el-Zour.

In Aleppo, where rebels fought troops to a stalemate last year, the two sides clashed near the air force intelligence building in the Zahra neighbourhood.

The state-run SANA news agency said an army unit killed "a number of terrorists and destroyed a convoy of cars that was transporting weapons, ammunition and terrorists" in Deir el-Zour.

SANA also said the military foiled an attempt by terrorists to detonate two car bombs in the southern province of Daraa, where the revolt against Assad started.