UK Defence Secretary Michael Fallon said there was an "inescapable logic" to extending UK military action across the border from Iraq in its fight against Islamic State (IS).

He also accused Russian President Vladimir Putin of "prolonging" the bloodshed in Syria by supporting President Bashar Assad's regime.

Asked about the risk of a collision or accidental clash with Mr Putin's forces, he told the BBC's Andrew Marr Show: "I am worried.
"When you have this activity you have on the Turkish border, which is a NATO border ... you have seen incursions into Turkish airspace."

But he added: "I don't think we should let Russia divert us for a moment from our focus against Isil. Don't let us forget that Isil beheaded British hostages, they were behind the slaughter of 30 British holidaymakers on a beach in Tunisia."

Mr Fallon reiterated the Government's commitment to holding a fresh Commons vote on Syria bombing raids, saying: "Isil is run from northeast Syria where Assad has not been in control for a couple of years. It's run from northeast Syria, its command and control is there, its logistics and supply routes in to Iraq. The others in the coalition have been striking at these targets, they would like us to take part but we don't yet have parliamentary authority to do so."

Mr Fallon criticised the Russians for killing hundreds of civilians in their airstrikes in Syria, and said 80% of their targets had nothing to do with IS. He denied Moscow had succeeded in "closing off" the skies over Syria, pointing out that the US and its coalition allies are flying missions over Raqqa in the northeast.

However, Alex Salmond, the former Scottish first minister, said if the UK extends airstrikes to Syria it would make "no significant difference" to the fight against IS.

"No-one, absolutely no-one, believes that diverting a few ageing Tornadoes from the strikes in Iraq to Syria is going to make any material difference to the military situation in Syria at the present moment," he told reporters.

He believes David Cameron could face defeat if he holds a vote on military action in Syria "because there is no credible argument that the Government is putting forward".

The Commons refused to back airstrikes in Syria two years ago. Labour leader Jeremy Corbyn opposes a broadening of military action against IS, but a number of his MPs are thought to be ready to vote yes to protect civilians.