-Islamic State jihadists have captured the western Iraqi town of Al-Baghdadi, putting them close to an air base where US troops are training Iraqi forces, the US military said Friday.

The sprawling Al-Asad air base came under attack Friday by IS militants but Iraqi soldiers repelled the assault, which involved suicide bombers, Iraqi and US officials said.

"We do assess that right now they have control of Al-Baghdadi," Pentagon spokesman Rear Admiral John Kirby told a news conference, adding they took hold of the town "in the past several days."

The town is located in Anbar province and is only kilometers from Al-Asad air base, where about 300 US Marines are stationed to assist Iraqi government troops.

A group of 20-25 IS fighters, wearing Iraqi army uniforms, carried out the attack on the base, according to Kirby. All of the militants were killed or died when detonating suicide bombs.

He said that "at no time were US troops anywhere near the fighting."

Kirby said the fall of Al-Baghdadi, one of the few towns that had remained under the Baghdad government's control, did not represent a major setback in the overall war effort.

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

"So this is an enemy that we still assess to be in a defensive posture."

He added: "It's one town. It's not all of Anbar. It's not all of Iraq.

"We need to keep it in perspective."