WESTERN-backed insurgents and al-Qaida attacked Syrian troops over the weekend in an apparent bid to preserve the Islamic State (Isis) stronghold of Raqqa.

But the army continued its advance towards al-Tabqah and the main road to Raqqa yesterday, taking the village of Abu Allaj.

The Russian centre monitoring the shaky ceasefire negotiated between Moscow and Washington in February reported on Saturday that 1,000 guerillas had attacked army positions south-west of Aleppo.

It said that fighters from the Free Syrian Army (FSA) and the al-Qaida-affiliated Nusra Front attacked the al-Breij district on the outskirts of the city from al-Ansari, an FSA-held area.

And the centre quoted local sources as saying that Turkish soldiers were seen among insurgent groups close to the fighting.

Nusra shelled the Kurdish YPG-held suburb of Sheikh Maqsoud on Friday, killing 40 civilians, while 17 more were killed in shelling of army-controlled districts on Saturday.

Late on Friday Russian Foreign Minister Sergey Lavrov said that the US was still objecting to air raids against Nusra on the basis that “moderate” groups were intermingled with them.

“They are telling us not to hit it [Nusra] because there is ‘normal’ opposition next to it,” Mr Lavrov said. “But that opposition must leave terrorists’ positions, we long have agreed on that.”

US State Department spokesman Mark Toner claimed that “a more complete effort needs to be made in order to distinguish between al-Nusra and the parties to the cessation.”

The YPG closed in on some 450-700 Isis militants in Manbij in northern Aleppo, taking the village of Baneyah Saghir, three miles to the north-east, as fierce fighting continued around grain silos two miles to the south.

YPG commander Abu Layla died of his wounds yesterday after being hit by an Isis sniper outside the town.