BEIRUT (REUTERS) - US-backed fighters besieging Islamic State in Iraq and Syria's final shred of territory in eastern Syria said they had pushed further into the enclave following clashes and air strikes by the US-led coalition.

"Our fighters advanced deep into areas controlled by the terrorist organisation and established a number of new points, following clashes in which terrorists sustained a number of deaths and injuries," a statement from the Syrian Democratic Forces (SDF) press office said.

It said 15 members of ISIS had been killed after they tried to attack SDF troops.

This story is developing.