BAGHDAD, March 7 (Xinhua) -- Six off-duty paramilitary Hashd Shaabi members were killed and 31 others wounded in an Islamic State (IS) attack on Wednesday on their convoy of buses in northern Iraq.

IS militants ambushed the convoy carrying dozens of the government-backed Hashd Shaabi members and opened fire on them on a main road near Makhmour area, a media office affiliated with the Iraqi Joint Operations Command said in a statement.

All the members under attack are Shiite Turkomans, who served in the northern province of Nineveh and, when the attack occurred, were on vacation heading to their hometown in Tuz Khormato area in the central province of Salahudin, said the statement.

A joint Iraqi police and army force rushed to the scene to secure the area and searched for the attackers, it added.

In December 2017, Iraq declared full liberation of its territories from the IS after security forces and Hashd Shaabi, backed by an anti-IS international coalition, recaptured all areas once seized by the extremist group.

IS remnants, however, have since melted in urban areas or resorted to deserts and rugged areas as safe havens, carrying out guerilla attacks from time to time against security forces and civilians.