Islamic State militants killed
A Kurdish People's Protection Units (YPG) fighter prepares weapons in the Assyrian village of Tel Jumaa, north of Tel Tamr town March 4, 2015. The Kurdish People's Protection Units (YPG) have seized two towns and dozens of villages from Islamic State (IS) in an offensive that got under way on Feb. 21 in the strategically important Hasaka province that borders IS-held areas in Iraq. Picture taken March 4, 2015. REUTERS/Rodi Said

BEIRUT (Reuters) - Unidentified gunmen killed at least 12 Islamic State militants in the eastern Syrian town of al-Mayadin in an overnight attack in an area near the Iraqi border controlled by ISIS, a group monitoring the conflict reported.

Gunmen on at least two motorbikes first opened fire on an Islamic State patrol before attacking Islamic State militants guarding a nearby courthouse, the Syrian Observatory for Human Rights reported.

A second group of gunmen meanwhile attacked an Islamic State checkpoint in the same town, killing and injuring an unknown number of the Islamic State militants, the Observatory reported.

Al-Mayadin is in the province of Deir al-Zor which is mostly controlled by Islamic State and is located about 60 km (40 miles) from the border with Iraq.

(Writing by Tom Perry Editing by Jeremy Gaunt)