British fighter jets took off from RAF Akrotiri in Cyprus early on Thursday shortly after Britain's parliament voted to bomb Islamic State targets in Syria, a Reuters witness said.

Four jets left in pairs within about an hour of each other from the airbase. Their destination was not immediately clear and there was no comment from British authorities.

RAF Akrotiri has been used as a launchpad for attacks on Islamic State targets in Iraq for just over a year, and late on Wednesday Britain's parliament broadened its scope for targets within Syria.

After more than 10 hours of tense debate, British lawmakers voted in favour of the air strikes, by 397 to 223.

In addressing parliament on Wednesday, British Prime Minister David Cameron said high-precision, laser-guided Brimstone missiles attached to the Tornado GR4 bombers would help to make a real difference by hitting the de facto Islamic State capital of Raqqa and its oil-trading business.

France and the United States are already bombing Islamist militants in Syria, while Russia has bombed mainly other rebels, according to conflict monitors and Western officials, in an intervention launched on Sept. 30 to bolster its ally, Syrian President Bashar al-Assad. The West says Assad must go.

Cyprus, which lies about 100 kilometres (60 miles) away from Syria, is the closest European Union member state to turmoil in the Middle East.

In October, two boatloads of Middle Eastern migrants, including Syrian refugees, washed ashore at Akrotiri, a jutting peninsula on Cyprus's southern coast.

Britain, a former colonial power, retains two sovereign military bases in Cyprus. – Reuters