Kabul, AFP—An improvised bomb explosion in southern Afghanistan has killed three NATO soldiers and two coalition civilians, the US-led International Security Assistance Force said on Saturday.

“Three International Security Assistance Force (ISAF) service members and two coalition civilians died following an improvised explosive device attack in southern Afghanistan today,” the military said in a statement.

The statement did not disclose the nationalities of the fallen soldiers and civilians in line with ISAF policy.

An ISAF spokesman in Kabul said the blast was a car bomb that targeted a military patrol in the insurgency-hit south. There were also Afghan civilian casualties, he added.

An Afghan official also confirmed that the blast was a car bomb on a NATO military patrol in Qalat city, the capital of southern Zabul province.

“An explosive-packed car went off this morning in Qalat city as a NATO convoy was passing. We heard it has caused heavy casualties,” the provincial official told AFP on condition of anonymity.

The attack is one of the deadliest to target US-led coalition forces this year, as their troops wind down their operation in the war-torn country ahead of a scheduled full withdrawal in 2014.