British airstrikes in Syria have killed or injured just seven Islamic State (Isis) militants, according to the Ministry of Defence. Only four attacks resulted in IS casualties since David Cameron won parliamentary support to extend airstrikes in December, the MoD revealed.

One militant was killed or injured at a checkpoint south of Raqqa on Christmas Day, after an RAF Reaper drone fired a Hellfire missile. Two more fighters from IS were hit on the same day in Tabqa, also with a Hellfire. On 11 January, two fighters were killed or injured in a Hellfire strike in Al Busayrah, while two more were hit by a Paveway IV guided bomb on 15 January.

The Prime Minister had stated that the high-precision Brimstone missile could make a "meaningful difference" to the international efforts to combat IS in Syria, however none of the RAF strikes have so far used the Brimstone.

The UK has focused on targeting IS infrastructure such as oil fields which provide revenue for the fighters. British Home Secretary Theresa May said in September that any British involvement in actions targeting the IS in Syria or Iraq would have a legal basis.

MoD sources said strikes targeting IS fighters were only carried out if there was no risk of civilians being injured.

An MoD spokesman said: "We are playing a crucial role in a campaign that will take time and patience. Using the right weapon for each scenario, RAF jets have struck Daesh (IS) almost 600 times. In Iraq we have helped to drive them out of Sinjar and Ramadi. In Syria, we have severely weakened them by targeting their key infrastructure."

The figures were released following a Freedom of Information request by the Huffington Post, Sky News reports.