Syrian government forces have inched closer to a key stop on a vital Islamic State supply line. In the battleground town of Tabqa, Islamic State fighters are caught between Russian-backed Syrian forces pushing from the southwest, and US-supported Kurdish and Arab fighters from the north.

Meanwhile, Russian Foreign Minister Sergei Lavrov has vowed to "actively support" Syrian troops around Aleppo from the air. He said Russia has waited long enough for Syria's moderate opposition to leave areas controlled by jihadist groups.