AKIPRESS.COM - The CIA says the Islamic State militant group may have up to 31,000 fighters in Iraq and Syria - three times as many as previously feared.

The new estimate was based on a review of intelligence reports from May to August, said BBC.

IS has seized vast swathes of Iraq and beheaded several hostages in recent months, leading to US airstrikes.

US Secretary of State John Kerry is visiting Turkey, seeking more support for action against IS.

On Thursday, 10 Arab countries agreed to help the US attack the group in both Iraq and Syria.

The CIA had previously believed that IS had about 10,000 fighters, BBC spokesman Ryan Trapani said.

"This new total reflects an increase in members because of stronger recruitment since June following battlefield successes and the declaration of a caliphate, greater battlefield activity, and additional intelligence", he added.

The revision comes a day after President Obama outlined a plan to "degrade and destroy" IS and to increase military support for allied forces engaged in fighting the group.

For the first time, he authorised airstrikes against the group in Syria.