Afghan security forces patrol at the Kunduz, Afghanistan on April 30, 2015. As the Army is losing ground to the Taliban in the north, Afghanistan is forming local militias and beseeching warlords to fight the insurgency. Reuters

At least 13 people were killed by gunmen who attacked a minibus in north Afghanistan on Saturday, local officials said.

All victims belonged to the largely Shiite Hazara ethnic minority that was persecuted by the hardline Sunni Taliban during their rule in 1996-2001, said Jafar Haidari, district governor of Zari in Balkh province, where the attack took place.

Last month gunmen kidnapped 12 Hazaras from a car in east Afghanistan, days after suspected Taliban fighters kidnapped and killed four Hazaras in the same province.

Nobody immediately claimed responsibility for Saturday's attack. Munir Ahmad Farhad, a spokesman for the Balkh governor, said an investigation team had been sent to the area.

Almost 5,000 civilians died in fighting and attacks in Afghanistan in the first half of 2015, the United Nations says, attributing around 70 percent of the killings to the Taliban.

The Islamist militants were ousted from power by a U.S.-led coalition in 2001 and are waging an insurgency against the foreign-backed government.

(Reporting by Bashir Ansari in Mazar-i-Sharif; Writing by Mirwais Harooni; Editing by Robin Pomeroy)