Syrian government forces backed by Russian air strikes have recaptured hills and villages from rebel groups on the outskirts of south-western Aleppo, a monitoring group and state-run media have said.
Rami Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights, said on Wednesday that the government had been launching a counterattack on areas captured by rebels in the past two days.
"Since the attack began and until Tuesday midnight, 40 civilians have been killed on both sides of Aleppo, among them 22 children," Abdel Rahman said.
About 50 rebels and dozens of regime troops have been killed since the assault kicked off on Sunday, according to the Observatory.
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Syrian state-run radio confirmed that government troops had started a "wide-scale counterattack" against rebels in south-west Aleppo.
"There are tit-for-tat attacks in all areas across south-western Aleppo, amid dozens of Russian strikes on areas which were taken by the rebels," Kenan, an activist based in the rebel-held Salaheddine neighbourhood of Aleppo, told the Dpa news agency via Facebook.
Government troops managed to seize two hilltops including Telat al-Mahroukat and the villages of Khweriz and al-Amriyeh, which the rebels took control of two days ago, the Observatory said.
Meanwhile, the New York-based Physicians for Human Rights (PHR) said on Wednesday that over the past week, Syrian government forces launched deadly air strikes against six hospitals in and around Aleppo.
The group said in a statement that this was the worst week for attacks on medical facilities in the region since the Syrian conflict began in 2011.
PHR said it had verified each attack.
All six facilities hit between July 23 and July 31 were major hospitals in Aleppo governorate, including a referral hospital just outside opposition-held eastern Aleppo and a paediatric clinic inside the city where four infants died after their oxygen supply was cut, the group said.
"Since June, we've seen increasing reports of attacks on civilians in Aleppo and strikes on the region's remaining medical infrastructure. Each of these assaults constitutes a war crime," said Widney Brown, PHR's director of programmes.
"Destroying hospitals is tantamount to signing thousands of death warrants for people now stranded in eastern Aleppo."