WASHINGTON, Feb. 13 (Xinhua) -- A group of Islamic State (IS) fighters on Friday got to the perimeter of an air base in Iraq where U.S. and coalition forces were training Iraqi forces before being killed by Iraqi armies, the Pentagon said.

About 25 IS fighters, some wearing Iraqi uniforms, launched an attack on al-Asad air base in Iraq's Anbar Province, Pentagon spokesman Rear Admiral John Kirby said at a regular briefing. No coalition casualties had been reported so far, said Kirby, cautioning that reports were still preliminary.

Kirby said that initial reports indicated that about 15 IS fighters tried to breach the perimeter of the air base after several suicide bombers detonated their vests.

Iraqi security forces patrolling the base killed all the fighters and U.S. Marines training Iraqi troops at the sprawling base were about 3.5 km away and were not involved in the fighting, he said.

The spokesman, however, declined to offer details on the degree to which the perimeter was breached.

Kirby also said IS fighters had taken control of al-Baghdadi, a town near the al-Asad air base.

"This is arguably the first in at least a couple of months, if not more, where they have had any success at all at taking any new ground," he said.

There are about 2,600 U.S. forces in Iraq, among whom about 450 are training Iraqi troops at three bases across the Arab country. Kirby said that American military trainees in Iraq were also well equipped to defend themselves when IS attacks were launched.