A Syrian monitoring group and an Iraqi official say clashes have erupted on the Syrian-Iraqi borders between Islamic State group militants and Iraqi Shiite fighters as the extremist group defends its last stronghold in the region.

The Britain-based Syrian Observatory for Human Rights says Saturday that IS militants repelled an attack by members of Iraq's Popular Mobilization Forces, a paramilitary group of Shiite fighters with Iraqi security forces. The Observatory says the attack took place inside Syria near the border town of Boukamal.

Spokesman for Iraq's Kataeb Hezbollah militia, Jaafar al-Husseini, tells The Associated Press his forces clashed with IS from Qaim, the Iraqi border town reclaimed from IS Friday. Al-Husseini says his militia fired rockets inside Syria but didn't cross. His militia built berms along the border to prevent militants from sneaking back.