Syria's army is poised to slice rebel-held eastern Ghouta in two as forces advancing from the east link up with troops at its western edge, a pro-Damascus commander said on Thursday.

The government, backed in the war by Russia and Iran, is seeking to crush the last major rebel enclave near the capital in a ferocious campaign that the aid agency Medicins Sans Frontieres (MSF) says has killed more than 1,000 people.

Rebels, who accuse the government of "scorched earth" tactics, said they were deploying more guerrilla-style ambushes in lost territory, trying to stop further advances.