Britain joined the US-led bombing campaign allegedly against ISIL Takfiri group in Syria on Thursday, with air strikes beginning just hours after a decisive parliamentary vote.

Britain joined the US-led bombing campaign allegedly against ISIL Takfiri group (so-called Islamic State in Iraq and Levant) in Syria on Thursday, with air strikes beginning just hours after a decisive parliamentary vote.

Royal Air Force planes based in Cyprus had returned from the "first offensive operation over Syria and have conducted strikes", a Ministry of Defense spokesman said early Thursday, following a vote Wednesday evening.

He refused to give details of the specific sites targeted.

Prime Minister David Cameron's government was backed by 397 lawmakers compared to 223 who opposed the bombing, giving him the strong mandate he said was ‘essential’ for military action.

Cameron welcomed the result of the House of Commons vote, writing on Twitter: "I believe the house has taken the right decision to keep the UK safe -- military action in Syria as one part of a broader strategy."

It was also immediately hailed by US President Barack Obama, who said the US would "look forward to having British forces flying with the coalition over Syria".

But during the debate, a wide range of MPs from all parties including main opposition Labor leader Jeremy Corbyn spoke out against air strikes.

Some 2,000 anti-war protesters also held a "die-in" outside parliament ahead of the vote during their second consecutive night of protest.

Corbyn condemned Cameron's "ill thought-out rush to war" and said his proposals "simply do not stack up".

However, Labor was also deeply split on the issue. Some 67 of its 231 MPs reportedly voted in favor of bombing, including 11 members of Corbyn's frontbench team.

Britain already had eight Tornado fighter jets plus drones involved in the US-led coalition striking ISIL targets in Iraq and will now deploy more jets.

Cameron has pledged that Britain joining air strikes on Syria will be matched by a major diplomatic push to resolve the crisis.

During the debate, the government also faced a string of questions about whether joining the international military action on Syria could make Britain more vulnerable to attacks from ISIL.

The last major attack on British soil was the July 7, 2005 bombings in which 52 people died.

And in June this year, 30 Britons were among 38 tourists killed in an attack at a holiday resort in Tunisia claimed by ISIL.

Officials say seven plots have been foiled by intelligence services in the last year alone. Cameron said this figure showed “it was right to take immediate action.”

"These terrorists are plotting to kill us and radicalize our children right now," he said. "They attack us because of who we are, not because of what we do".