DAMASCUS, May 11 (Xinhua) -- Heavy airstrikes and shelling targeted rebel positions in the northern countryside of Hama province and the nearby countryside of Idlib province on Saturday as part of an ongoing Russian-backed campaign, a war monitor reported.

The Russian and Syrian warplanes started the 12th day of escalation with airstrikes and ground shelling on rebel positions in northern Hama and the southern countryside of Idlib, the Syrian Observatory for Human Rights said.

The Britain-based watchdog group said that the airstrikes renewed after midnight Saturday.

The report said that the Syrian army made progress and captured key areas from the rebels of Hayat Tahrir al-Sham (HTS), the umbrella group of the al-Qaida-linked Nusra Front.

Areas in the countryside of Hama, Idlib and the western countryside of Aleppo are included in the de-escalation zones deal which was reached between Russia and Turkey in September 2018.

The deal failed to materialize as the HTS expanded in Idlib and started attacks on Syrian military positions instead of withdrawing from the designated zone which combines Idlib with Hama and Aleppo countryside.