BEIRUT -- Syrian government forces attacked rebels with helicopter gunships in the heart of Damascus on Tuesday, escalating a campaign to crush their opponents as clashes spread to new areas, illustrating the rebels' growing reach.
Cracks of gunfire and explosions echoed inside the capital for a third day, including a firefight near the country's parliament, in an unprecedented challenge to government rule in President Bashar Assad's seat of power.
Neighboring Iraq called on its citizens living in Syria to return home, as the fighting overshadowed another round of diplomatic maneuvering to end the civil war, with special envoy Kofi Annan in Moscow in an attempt to rescue his faltering peace plan.
Plumes of gray smoke billowed over the Damascus skyline and helicopter gunships strafed the area, activists said -- a sign the regime is growing desperate to push the rebels away from the heavily guarded capital.
Terrified families fled the city or said they were prepared to leave at a moment's notice. Residents said they were packing "getaway bags" in case they had to run for their lives.
"My bag has my family's passports, our university degrees, some cash and medicine," a 57-year-old father of two said, asking that his name not be used for fear of reprisals. "It is very hard to imagine leaving your home and everything you worked to get, but it's a matter of life and death."
Clashes were concentrated in the neighborhoods of Kfar Souseh, Nahr Aisha, Midan and Qadam -- a mixture of lower- and middle-to-upper-class districts in the city's southwest where street battles first erupted Sunday. Heavy clashes were also reported in Qaboun, a neighborhood in northeast Damascus.
"The streets are completely empty, the shops are closed. People are terrified of what's next," said Omar Qabouni, an activist in Qaboun. He said eight people were killed Tuesday in mortar and tank shelling by government forces. He estimated that about 300 rebels were taking part in the fighting.
Activists and residents said the fighting also reached new areas Tuesday, with brief firefights erupting in Sabeh Bahrat Square, Baghdad Street and Sahet Arnous in downtown Damascus, about 400 yards from the Syrian parliament.
The clashes broke up quickly as the rebels fled, but were a significant indicator of the rapidly spreading violence and the deep reach of the rebels as they become more confident and better armed.
The Damascus clashes were a sign the civil war was likely to worsen as the Syrian regime struggles to halt the opposition's growing momentum.
"The Syrian army's increasing deployment of artillery and helicopter gunships underscores that the regime is prepared to escalate its use of force concurrently with the armed opposition's improving capabilities," wrote Torbjorn Soltvedt, senior analyst at Maplecroft, a British-based risk analysis company in a report released Tuesday.
Syria's state-run news agency said troops were still chasing "terrorist elements" who had fled from Nahr Aisha to Midan. The Syrian regime refers to armed rebels as terrorists.
Troops also threw up multiple checkpoints and were searching cars in an effort to seal the capital off from rebellious areas in the suburbs.
"I can hear cracks of gunfire and some explosions from the direction of Midan," Damascus-based activist Maath al-Shami said via Skype. "Black smoke is billowing from the area."
Although the uprising began in March 2011 with largely peaceful protests, a government crackdown prompted many in the opposition to take up arms.
Now, the conflict is a full-blown civil war, and activists say more than 17,000 people have been killed. There are fears the violence and chaos could spread across the region.