BAGHDAD, Oct 24 (Reuters) - U.S.-backed Kurdish fighters blocked an offensive launched by Islamic State on Monday in Sinjar, a Yazidi territory west of Mosul, a provincial official in the region said.

The attack was an apparent bid to distract Iraqi forces attacking Mosul, Islamic State's last major city stronghold in Iraq.

Islamic State confirmed in an online statement having carried out a suicide attack on a peshmerga position at the western entrance of Sinjar.

"It was the most violent attack on Sinjar since a year ago," Yazidi provincial chief Mahma Xelil told Reuters.

Islamic State committed some of its worst atrocities in Sinjar when it swept through the Yazidi region two years ago, killing men, kidnapping children and enslaving women. Kurdish fighters took back the region a year ago.

Xelil said at least 15 militants were killed in the two-hour battle and a number of vehicles they used in the attack were destroyed, while the peshmerga suffered two wounded.

Islamic State said two peshmerga vehicles were destroyed and all those on board were killed.

Iraqi and Kurdish forces launched an offensive on Mosul a week ago, with air and ground backing from the U.S.-led military coalition.

It was from Mosul's Grand Mosque in 2014 that Islamic State leader Abu Bakr al-Baghdadi declared a caliphate over parts of Syria and Iraq.

The region of Nineveh around Mosul is a mosaic of ethnic and religious groups - Arabs, Turkmen, Kurds, Yazidis, Christians, Sunnis, Shi'ites - with Sunni Arabs the overwhelming majority.

The Yazidis are a religious sect whose beliefs combine elements of several ancient Middle Eastern religions and who speak one of the Kurdish languages. They are considered infidels by the hardline Sunni Islamist militants.

(Reporting by Maher Chmaytelli; Editing by Dominic Evans) ((maher.chmaytelli@thomsonreuters.com; +9647901917030;))