Sinn Fein MP Francie Molloy has incensed unionists in the North in a tweet linking Britain to murder.

The Belfast Telegraph reports Molloy posted the comment after the House of Commons voted in favour of extending Britain's bombing campaign against the Islamic State to Syria.

Responding to a tweet by Deputy First Minister Martin McGuinness, he wrote: "Brits back to what they do best, Murder."

Brits back to what they do best, Murder. https://t.co/oT1fsrDdpJ

— Francie Molloy (@FrancieMolloy) December 1, 2015

DUP MP Gregory Campbell called the quip "grossly offensive" and alluded to the IRA's history of violence.

"If Sinn Féin feel strongly about the aerial attacks into Syria they could have taken up their seats," he said, speaking to BBC Talkback

Ulster Unionist MP Danny Kinahan added to the criticisms: "It reveals a deeper mindset within the psyche of some Sinn Féin members which seems to be an irrational hatred of all things British apart from pounds sterling, Westminster expenses and hospitality at Windsor Castle."

Sinn Féin has remained silent on the tweet, however MLA Pat Sheehan said the decision to extend bombing would "only add to the cycle of violence gripping the country and indeed further afield."