Activists in Idlib said that Syrian and Russian warplanes launched a series of airstrikes on Monday on areas taken over by rebels in north-west Syria during a surprise offensive.

According to the White Helmets, a Syrian civil defence organization which works in rebel-held areas, there were civilian casualties, and numerous residential buildings were destroyed.

An alliance of insurgents led by the Islamist group Hayat Tahrir al-Sham (HTS) launched an offensive in north-west Syria last week on Syrian government areas and took control of Aleppo, the country’s second-largest city.

The Syrian Observatory for Human Rights, a UK-based war monitoring group, said the airstrikes by Syria and Russia targeted areas controlled by rebels in Aleppo, the countryside of Hama and Idlib.

The observatory has been documenting violence in Syria since the uprising against Syria.

President Bashar al-Assad, in 2011, said that over five days of clashes between Syrian government forces and rebels, more than 440 people had been killed.

It said that the dead included more than 60 civilians.

Syrian government sources told dpa that its forces had launched a counter-attack and had retaken most regions that the rebels took in the countryside of Hama over the weekend.

The observatory said that pro-Iranian Iraqi militia fighters had crossed from the al-Bou Kamal border with Iraq in eastern Syria over the past 24 to help their Syrian government allies.

It estimated that 200 fighters had crossed the Iraqi-Syrian border since Sunday.

Iran and Russia have been the main backers of al-Assad.

(dpa/NAN)