LONDON - Britain said on Thursday it was sending armed drones to Iraq to help it fight Islamic State militants and support British Tornado aircraft already conducting air strikes.

Britain is part of an international coalition, led by the United States and including Middle-Eastern partners, which is trying to counter the advance of IS fighters who have seized large amounts of territory in Iraq and Syria.

The "Reaper" drones, built by privately owned US firm General Atomics, were being re-deployed from Afghanistan, Defence Secretary Michael Fallon said in a written statement to parliament.

"As the UK's only armed remotely piloted aircraft, Reaper will add to the strike capability we are already providing," Fallon said.

Their use would be bound by the existing rules of engagement, he added, meaning that their operations would only take place in Iraq.

The British parliament voted last month to approve air strikes against IS in Iraq, after a request from the Iraqi government, but is not conducting air strikes in Syria.