Syrian government forces are reportedly bombarding eastern areas of the capital, Damascus, a day after rebel fighters launched a surprise offensive.
Activists said opposition-held parts of Jobar had been targeted repeatedly by aircraft and artillery, amid fierce clashes along the frontlines.
Air raids were also reported in neighbouring Qaboun and Arbin.
Earlier, state media said the military had recaptured all of the territory it had lost in Sunday’s rebel assault.
Free Syrian Army factions and allied jihadist groups were involved in the attack on government-controlled Jobar and Abbasid Square, only 1.2km (0.7 miles) north-east of the Old City.
The Syrian Observatory for Human Rights, a UK-based monitoring group, said pro-government fighters and 21 rebels and jihadists were killed in the fighting.
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There were no immediate reports of any casualties from Monday’s air strikes, but Syrian Observatory director Rami Abdel Rahman described them as “intense”.
“The government and allied forces have retaken the initiative and are striking the groups that launched yesterday’s assault,” he told AFP news agency.
The Local Co-ordination Committees, an opposition activist network, reported that Jobar had been hit by dozens of air strikes, as well as shell- and rocketfire.
Qaboun and Arbin, to the north and north-east, were also under attack, it said.
The official Sana news agency said troops had been carrying out a number of operations against jihadists from Hayat Tahrir al-Sham, a new alliance created by al-Qaeda’s former affiliate in Syria, and allied groups north of Jobar.
All members of the groups who had infiltrated government-controlled areas had been eliminated and their equipment destroyed, it cited a military source as saying.
Sana also said the situation in the area attacked on Sunday was back to normal.
Sky News Arabia reported that hundreds of residents had fled to the city centre, but AFP correspondents confirmed that activity in Abbasid Square was at normal levels on Monday and that roads sealed off by troops had been reopened.
The fighting comes only days before another round of UN-brokered peace talks in Geneva aimed at finding a political solution to Syria’s six-year civil war.
Government and rebel factions agreed to a nationwide cessation of hostilities in December, but both sides have accused each other of repeated violations. Tahrir al-Sham and the rival jihadist group, Islamic State, are excluded from the truce.
Syria conflict: Aircraft pound rebel-held eastern Damascus}