CIA claims number of ISIS fighters has trebled to 31,500 since June

The Central Intelligence Agency, has reportedly said that the number of Islamic State of Iraq and Syria (ISIS) fighters has increased three times the previous estimates.

A CIA spokesman said on Thursday that the militant group can muster 20,000 to 31,500 fighters across Iraq and Syria, reported the CNN.

The spokesman said that the new figures reflect the increased recruitments since June after several battle field successes, declaration of a caliphate and additional intelligence.

The report also quoted a CIA source as saying that about 2,000 westerners have joined the ranks of the ISIS from more than 80 countries.

Analysts and the United States officials had earlier estimated that 10,000 fighters have joined the ISIS as it advanced across Iraq.

The news came a day after the United States President Barack Obama spelled his plan to "degrade and ultimately destroy" the militant group in Iraq and Syria.