Tornado bombers took off from the RAF Akrotiri air base in Cyprus and made strikes on targets in Syria, the source said. The bombers are back at base.
“A strike was made from over Syria,” said the source, who spoke on condition of anonymity.
The source declined to give further operational information about the targets or the number of aircraft involved, citing national security.
A Reuters witness in Cyprus saw four jets leaving in pairs from the air base within an hour of each other. Two have since returned.
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, members of parliament voted in favour of the air strikes, by 397 to 223.
In addressing parliament on Wednesday, 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, 100 km (60 miles) 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.