Syrian forces on Wednesday fired artillery and rocket barrages at the northern Damascus suburb of al-Tel in an attempt to seize the town from rebels, causing mass panic and forcing hundreds of families to flee the area, residents and opposition activists said.

The 216th mechanized battalion headquartered near Tel started bombarding the town of about 100,000 people at 3:15 A.M. at the rate of one projectile every minute, and initial reports indicated that residential apartment blocks were being hit, they said.

Opposition sources said that rebels destroyed an army roadblock that had cut off the Tel-Damascus road, and that most people were fleeing north into the nearby Qalamoun Mountains.

"Military helicopters are flying now over the town. People were awaken by the sound of explosions and are running away," Rafe Alam, one of the activists, said by phone from a hill overlooking Tel.

"Electricity and telephones have been cut off. Tel had been considered a safe haven and thousands of families from Homs and Damascus suburbs like Douma took refuge over the past few months in Tel," said Alam, who is using a pseudonym because he fears for his safety.

Tel, located eight kilometers (five miles) north of Damascus, is a conservative Sunni Muslim town that relies on remittances from expatriates in Saudi Arabia, who work there mostly as skilled laborers in the construction sector.

The town fell into rebel hands last week along with several districts in the capital and on its outskirts after a bomb killed four of President Bashar Assad's top lieutenants.

Meanwhile, the border gates between Turkey and Syria are to be closed on Wednesday, Turkish Customs and Trade Minister Hayati Yazici was reported as saying by broadcaster NTV.

The move comes after Syrian rebels seized control of several border gates along the frontier with Turkey in their 16-month-old uprising against President Bashar Assad. The decision to close the gates could not immediately be confirmed.

Early Wednesday, Syrian government moved additional troops to Aleppo after clashes with rebels escalated in and around the country's largest city, according to a news report.

About 2,000 soldiers along with tanks and artillery were being moved from Idlib, 70 kilometers to the south-west, US broadcaster CNN quoted an official of the rebel Free Syrian Army as saying.

Fighting across Syria killed about 120 people Tuesday, the London-based opposition Syrian Observatory for Human Rights said.

An estimated 21 people were killed in Aleppo, the opposition Local Coordination Committees of Syria were quoted as saying by CNN. The group put Tuesday's country-wide toll at 133.

"Helicopter and tank shells are falling on areas in the outskirts of Aleppo, which came under the control of the rebels," activist Abu Haytham al-Halabi said by phone.

Government forces were seeking to quell a mutiny in Aleppo's central prison, where eight people were killed, the observatory said.

The Free Syrian Army described the mutiny as "the first step toward the liberation" of Aleppo.

U.S. Secretary of State Hillary Rodham Clinton said Tuesday that the crisis in Syria was "accelerating" and that the opposition must ready for a post-Assad transition.

The offensive in Aleppo came as the Free Syrian Army warned that President Bashar al-Assad's regime had moved chemical weapons to airports, Qatar-based broadcaster Al Jazeera reported.