The Ministry of Defence (MoD) said an RAF Reaper drone had fired a Hellfire missile at Islamic State forces laying homemade bombs north of Baghdad.
An RAF Reaper drone was involved in coalition missions near Baiji, the site of Iraq’s largest oil refinery.
The Government has also announced the Reapers will fly surveillance missions inside Syrian airspace.
The MoD said, “A series of coalition missions were conducted near Bayji, north of Baghdad, where Isis terrorists were laying improvised explosive devices. The Reaper remotely piloted aircraft system, using procedures identical to those of manned aircraft, successfully attacked the terrorists using a Hellfire missile. UK Reaper continued to provide intelligence, surveillance and reconnaissance assistance to coalition aircraft which enabled them to conduct further strikes.”
The UK launched its first air strikes against IS targets in Iraq on 30 September – four days after Parliament approved military action. It has also sent military trainers to help local forces in their efforts to halt the advance of IS.
The MoD said RAF Tornado jets were also involved in airstrikes near the oil refinery in Baiji over the weekend. The town, about 200km (130 miles) north of the capital Baghdad, was seized by militants in June but they failed to capture the refinery.
An RAF aircraft also destroyed a shipping container west of Baghdad, on Sunday morning. The MoD said the container was “used by the terrorists to store equipment to support extortion and control of the local population”.
On Sunday, officials said Iraqi government forces had regained large areas of the town.