The Syrian army is preparing to launch a "huge" operation against the last rebel-held town in eastern Ghouta unless the Jaish al-Islam insurgent group agrees to hand over the area, a pro-Syrian government newspaper reported on Wednesday.

The group has been negotiating about the town of Douma with the government's main ally Russia. But a commander in the regional alliance fighting in support of President Bashar Assad said late on Wednesday that the rebels' position had been rejected.

"The negotiations stopped. Most of the militants have set out big conditions, and the Russians and the Syrians have refused them," the commander said.