The Syrian army and its allies launched a major attack on insurgents south of Aleppo, described as the fiercest government assault in the area since an agreement to ease the fighting came into effect in February.
Fighting south of Aleppo in recent days has put further strain on the already widely violated ceasefire deal brokered by the US and Russia with the aim of launching a diplomatic process towards ending the five-year-long war.
The indirect talks organised by the UN are struggling with no sign of compromise over the main issue dividing the sides: the future of President Bashar al-Assad. A second round of talks is due to begin on Monday in Geneva.
Rebels described intense air strikes in the southern Aleppo area where the Al Qaeda-linked Nusra Front shot down a Syrian warplane on Tuesday and captured its pilot.
Nusra Front, which along with Islamic State is not part of the ceasefire, last week attacked and captured a town in the area, killing dozens of Syrian soldiers and their allies, among them 11 members of the Lebanese Shi’ite group Hezbollah.
A statement from the Syrian army and its allies said they were targeting armed groups in areas south of Aleppo, supported by “heavy and concentrated air strikes”, the website of the Hezbollah-controlled Al-Manar reported.
Each side accuses the other of seeking to wreck the cessation of hostilities agreement that has slowed the war across many of the major frontlines of western Syria but not stopped it entirely. Though Nusra is not part of the deal, its fighters are deployed near rebel groups that are.
Syria’s crisis erupted five years ago with protests against Assad which were put down with force. It descended into a civil war which has killed more than 250,000, drawn in global military powers and helped Islamic State establish its self-declared caliphate. Nearly 5mn refugees have been driven abroad.
Russia’s six-month-old intervention in Syria has helped to swing military momentum in Assad’s favour, reversing last summer’s gains by insurgents including Western-backed rebels and helping government forces to drive Islamic State out of the ancient city of Palmyra.
The recapture of Palmyra and its military airport, in the central Syrian desert, opened up the road further east to the Islamic State bastions of Deir al-Zor province and Raqqa. Any offensive on Deir al-Zor or Raqqa, however, would probably need significantly more firepower than the Palmyra assault.
A rebel said the government attack south of Aleppo was the heaviest in that area since the truce agreement came into effect. Hany al-Khaled of the Sham Revolutionary Brigades group, an affiliate of the Levant Front, said his group had taken part in repelling the attack, and Shi’ite militias fighting with the government had suffered heavy losses.
The Syrian Observatory for Human Rights, a British-based organisation that tracks the war, said air strikes, artillery and rockets were being used in an attack aimed at recovering Telat al-Eis, the town seized in the Nusra Front-led assault.
Opposition official Asaad al-Zoubi said the truce was “in danger of ending” due to government violations.
“There are still hiccups in the ceasefire that are happening from day to day,” the US Pentagon said in a press briefing on Wednesday.
In addition to the 11 Hezbollah fighters killed, 43 Syrian soldiers died in last week’s Nusra attack, sources familiar with the details said. Hezbollah’s support has been crucial to Assad in the conflict, together with backing from Shia militias mobilised from Iran and Iraq and Russian air power.
Russia last month withdrew some of its warplanes from Syria, where it has been bombing in support of Assad since Sept. 30.
Indicating an expansion of Iranian support, an Iranian military official said on Monday that Tehran has sent commandos from the regular Iranian army to Syria as advisers. So far, Iran’s military support to Damascus has mostly been supplied by its Islamic Revolutionary Guards Corps.