Image copyright Reuters Image caption Islamic State already controls parts of Libya and MPs warn it could spread further

MPs have warned of the risk of so-called Islamic State proliferating into an "international movement" if it is forced out of Iraq and Syria.

The Commons Defence Committee said there was a danger of IS, also known as Daesh, forming regional offshoots, like al-Qaeda before it, in Africa and Asia.

IS-backed fighters are active in Libya and have mounted attacks in Turkey.

Speaking in Iraq, Defence Secretary Michael Fallon said the UK would not "walk away" once Daesh was defeated.

During a visit to Baghdad, Mr Fallon said militants controlled less than 10% of Iraqi territory and could be pushed back beyond Iraq's borders within months.

The UK has been taking part in air strikes against Islamist militants in Iraq since 2014 and Parliament authorised their extension to Syria last year.

In its report, the committee said there had been 550 RAF missions in Iraq since December 2015 and 65 in Syria.

'Credible forces'

Substantial progress was being made in Iraq, it said, where the UK was helping government forces regain and hold on to territory and also playing a pivotal role in training Iraqi troops

But it expressed concerns that unless there were far-reaching political and economic reforms, it would leave the space for Daesh to spring back or be replaced by other Islamist groups.

The situation in Syria, it said, was more "complicated" given the nature of the Assad regime and a lack of clarity over the opposition forces operating on the ground.

Image copyright AP Image caption The UK had trained more than 25,000 Iraqi troops, Mr Fallon said

The committee said it had requested details from the government about opposition groups in Syria in light of David Cameron's comments last year that there were 70,000 moderate forces which were neither aligned with Islamic State nor the regime.

The MPs said the government's unwillingness to identify all the groups was understandable given the risk of intelligence falling into the regime's hands.

But they said the government's failure to provide details could undermine its claim that the action in Syria was in support of "credible moderate ground forces".

The disparity between the effort being put into military and stabilisation efforts was "concerning", said the committee, which added that the low priority being given to diplomatic and development work "does not reassure us about Iraq's long-term future".

Network of affiliates

It also called on the government to put more information about the targets for air strikes in Syria into the public domain, in order to "justify and validate" its policy of military action.

Julian Lewis, the Conservative MP who chairs the committee, said the UK must focus on the long-term risks.

"If Daesh transforms itself into an international movement or a network of affiliates - like al-Qaeda before it - which can survive the loss of territory - the UK government approach will need to adapt," he said.

Image copyright Getty Images Image caption The rise of IS has reinvigorated jihadist activity in Indonesia

"For example, if Daesh is defeated in the Middle East but then grows strong in Africa, the current strategy will require major revision.

"Assuming Daesh is squeezed out of both countries, we have to focus too on what happens next - both in other countries to which Daesh may migrate and in Syria especially where there is no shortage of other Islamist groups, just as dangerous, which are planning to take control."

The government said it accepted Daesh could not be disbanded by force alone and its strategy encompassed cutting off its sources of income, challenging its propaganda and curbing the flow of foreign fighters.

The UK remained committed to supporting Iraq, Mr Fallon said, whatever the nature of the threat its faced.

"What I want to be clear about is that after Daesh is defeated in Iraq, Britain is not walking away," he said.

"After the defeat of Daesh it (support) is likely to cover areas like further army training, secondly advice on security sector reform, and thirdly work on counter-terrorism."