Syrian warplanes hammered opposition-held neighbourhoods of Damascus on Monday after regime forces pushed back a surprise assault that saw rebels try to fight their way into the city centre.
Rebels and allied militants, led by former Al-Qaeda affiliate Fateh al-Sham Front, launched an attack early Sunday on government positions in east Damascus, initially scoring key gains.
But forces loyal to President Bashar al-Assad drove them back by nightfall and began a fierce bombing campaign on Monday morning.
"There have been intense air strikes since dawn on opposition-held positions in Jobar from which the offensive was launched," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
"The government and allied forces have retaken the initiative and are striking the groups that launched yesterday's assault," he added.
Abdel Rahman said it was unclear whether regime forces or their Russian allies were carrying out Monday's raids on Jobar.
Control of Jobar -- which has been a battleground for more than two years -- is divided between rebels and allied militants on one side, and government forces on the other.
On Sunday, opposition fighters seized several buildings in Jobar before advancing into the neighbouring Abbasid Square area -- the first time in two years that the opposition had advanced so close to the capital's centre.
The clashes left dead at least 26 regime forces and 21 rebels and militants, Abdel Rahman said, but he did not have an immediate toll for Monday morning's air strikes.
Sniper fire and air strikes were heard across the city on Sunday as civilians cowered inside their homes and schools announced they would close because of the violence.
But by Monday, the front line had been pushed back, and AFP correspondents said activity in the typically bustling Abbasid Square was returning to normal levels.
Airplanes could still be heard circling above but many of the roads that had been sealed off by army troops the previous day were reopened.
According to the Observatory, government forces managed to recapture most of the territory overrun by rebels in their assault.
Opposition forces still controlled several key points in an industrial zone lying between Jobar and the besieged northeastern district of Qabun to the north, according to the Britain-based monitor.
State news agency SANA said Syrian government troops were targeting rebel bases around Jobar on Monday.
"The military operations north of Jobar targeted the areas from which the terrorists set out, and a large number of them were killed," it said.
The Islamist Faylaq al-Rahman rebel group and the Fateh al-Sham Front -- known as Al-Nusra Front before it renounced its ties to Al-Qaeda -- have a presence in Jobar.
Syria's conflict erupted in March 2011 with protests against Assad's rule but has morphed over the years into a complex civil war.
More than 320,000 people have been killed and millions more have been displaced by the conflict.