The Syrian government forces, backed by Russia, have unilaterally ceased firing in the northwestern Idlib province, the last major rebel-held territory, Moscow’s defence ministry said.
However, opposition activists said shelling and air attacks continued on Sunday despite the announcement.
Fighting erupted in northwestern Syria last month and shattered a truce negotiated by Russia and Turkey late last year.
Syrian government forces intensified their attacks on Idlib, which is home to three million people, late in April, as the United Nations and rights groups warned of an humanitarian catastrophe.
The offensive by the Syrian army and its allies uprooted more than 150,000 people, the UN said.
In a brief statement on Sunday, the Russian Defence Ministry’s Center for Reconciliation of the Warring Sides in Syria said government forces had ceased firing as of midnight.
It described the move as unilateral but did not give any further details.
However, the pro-government Syrian Central Military Media said government forces responded to shelling by rebel fighters on Sunday on the edge of Idlib, according to the Associated Press news agency. It gave no further details.
Meanwhile, the Syrian Observatory for Human Rights, a Britain-based war monitoring group, reported an air attack on the town of Khan Sheikhoun, saying it inflicted casualties.
The opposition’s Syrian Civil Defence also reported shelling near the town of Jisr al-Shughour without reporting any casualties.
Russia has firmly backed President Bashar al-Assad’s government in the eight-year civil war, while Turkey has supported some of the rebel groups, but the two sides had worked together to try to contain fighting in the country’s northwest.
The deal came after another escalation between government forces and HTS fighters in late 2018. Both Russia and Turkey list the HTS as a “terrorist” organisation.
The Sochi agreement prevented government forces from launching a major military operation on Idlib and protected the so-called “de-escalation zone” agreed on between Russia, Iran and Turkey in 2017.
Since the Sochi agreement, Moscow at various times said that “terrorist groups” were operating in the zone.
Russia has also been piling pressure on Ankara to start an operation in Idlib after Turkey’s failure to get the HTS fighters out of the “de-escalation zone”.
Turkey has said the recent Syrian government attacks violated the Sochi agreement.