Syrian rebels launched a massive attack on Damascus Sunday amid government bombardments of rebel-held areas as a new round of U.N.-brokered peace talks was scheduled to begin in Geneva this week.

The presidential palace was rocked by explosions, Twitter user Eboumhna Remaly reported.

Both moderates and jihadist rebels were reported involved in the attack about 1.2 miles from the heart of the Old City.

Read: Is US Responsible For Syria Mosque Bombing?

The BBC reported two suicide car bombs exploded in the Jobar district, near the capital’s center, as rebels attempted to storm government defenses. Syrian state media also reported the rebels used tunnels to launch their attack.

Steady shelling and sniper fire were reported across the city as factions allied with al Qaeda affiliate Jabhat Fateh al-Sham targeted government positions, Al Jazeera reported.

Read: Who Is Abu Khayr al-Masri? Al Qaeda Second In Command Killed

Two large car bombs went off about 5:20 a.m., local time, near Jobar. Tahrir al-Sham, an umbrella group for hardline fighters, claimed responsibility.

Reuters reported the army deployed tanks in adjacent neighborhoods.

"The streets are empty and the army has despatched dozens of troops in the streets, and tanks are being moved. The sounds of mortars from Jobar have not stopped," a resident of the nearby Tijara district, who asked not to be named, told Reuters.

The Syrian Observatory for Human Rights said the attack was launched to relieve pressure from government forces in Barzeh, Tishreen and Qabun districts.

The observatory said rebels captured several industrial sites and buildings east of the capital as a result of the attack.

The opposition holds only a few areas of Damascus. The fighting targeted the government-controlled gap between Jobar and Qaboun. The ultraconservative Ahrar al-Sham rebel group claimed victory, Al Jazeera said. But state media said the attack had been repelled.

AFP reported the army had blocked access to Abbasid Square.

Schools announced they would be closed Monday for fear the shelling would continue.

A suicide bomber last Wednesday killed at least 31 people in the main court complex, and 20 more were injured in another attack at a restaurant later in the day, marking the sixth anniversary of the uprising against President Bashar Assad.

Fighting has continued across Syria despite a December ceasefire agreement.

Peace talks among Syrian factions are scheduled to begin Thursday in Geneva.