Tackling the threat of Islamic State (IS) requires a coherent response and not the "knee-jerk" extension of Syrian air strikes, Alex Salmond said today.

The SNP's foreign affairs spokesman said diplomatic efforts need to be better co-ordinated and look at the areas of propaganda and the group's financing.

This week in the Commons, Defence Secretary Michael Fallon began laying out the case for extending RAF air strikes into Syria in the wake of the Tunisia terror attack.

Talking on the BBC's Sunday Politics programme, Mr Salmond said military intervention can be justified in some circumstances but it is "extraordinarily difficult to work out who you should be bombing" in Syria.

He said: "You shouldn't just engage in aerial conflict and believe that's a solution because clearly the evidence shows that it's not.

"I think a military intervention is justified when it's legally based, when it's conducted with a range of allies and when it can prove to be effective.

"We need a coherent response... not just a knee-jerk addition to an air campaign that's being conducted already."

The former first minister of Scotland outlined what he believes is an appropriate response to the threat of IS, which he referred to by its alternative name of Daesh.

He said: "One is to recognise that this is basically a battle of ideas, different views of the world, and to realise that the propaganda campaign is of huge importance.

"Secondly, a much more organised targeting of the financial basis of Daesh, to realise that this is an organisation loose in terms of aspects of its command and control but nonetheless hugely well-funded because of its economic control of oil fields. Surely much more could be done on that level.

"Thirdly, a much more sustained diplomatic offensive. It's incredibly difficult to line up the forces who are against Daesh but a much more co-ordinated response on that front might be useful, instead of knee-jerk reactions like we saw in the Commons this week."

Asked if he would support the deployment of UK and US special forces, he replied: "The circumstances would have to be a lot more substantially-based than what we heard in the House of Commons this week."

The most effective fighting force against IS on the ground at the moment are Kurdish forces, the MP told the programme.

He said: "I would be interested in and supportive of an examination of how they can be given, let's say, as much military assistance as we've given to the Iraqi army who unfortunately have run away from key battles and left their weapons to be taken up by the Daesh organisation."