British bombers have attacked oilfields in eastern Syria, Defence Minister Michael Fallon says, hours after parliament approved the bombing of Islamic State targets in the country.

“I approved yesterday a series of targets in the Omar oilfields, well heads… the Tornados were successful in striking those targets,” Fallon told the BBC on Thursday.

Britain has also sent eight more warplanes to its base is Cyprus to join air strike missions against IS in Syria, Fallon said.

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“Today we are doubling our strike force. The additional eight aircraft being sent to (RAF air base) Akrotiri, are now in the air and on their way,” he told BBC radio.

The additional planes were six Typhoon fighters and two Tornados, he said.

The British Ministry of Defence said on its Twitter feed that British jets had hit al-Omar oil fields as part of the campaign against IS.

Parliamentarians spent more than 10 hours debating the issue. Photo: AAP

A Reuters witness in Cyprus saw four jets leaving in pairs from the air base within an hour of each other.

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

Meanwhile war planes from a US-led coalition carried out overnight strikes on oil-producing areas in an IS-held part of eastern Syria, a group monitoring the war said.

The Syrian Observatory for Human Rights did not identify the war planes as British but said coalition jets launched raids on Jafra, Tanak and al-Omar areas in Deir al-Zor province.

The Observatory, which tracks the conflict using sources on the ground, said there were so far no details about any casualties.

France and the US 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 September 30 to bolster its ally, Syrian President Bashar al-Assad.