KABUL (AP) – A bomb inside a package left at a checkpoint in Afghanistan’s capital exploded early Friday when police opened it, killing one officer, police said.

Police stopped a man walking with a large package in southern Kabul before dawn, and the man quickly dropped the box and ran off, said Ahsib Arian, the district police chief. An officer was killed when he looked inside the box, he said.

Meanwhile, Taliban militants released the father of Afghanistan’s education minister after holding him hostage for four days.

Two militants on motorbikes seized Education Minister Farouq Wardak’s father in central Wardak province Monday.

Khoja Mir, 80, was released in neighboring Ghazni province early Friday with the assistance of community elders who pressured the kidnappers to set him free, said Ghazni Police Chief Gen. Khialbaz Sherzad.

Kidnappings of wealthy Afghans have spiked over the last year, often carried out by criminals and militants seeking money or political leverage.

Both the police chief and another of Mir’s son’s, Sher Wali Wardak, said he was released without any exchange of money.

Sher Wali Wardak praised the government for its quick reaction, and said his father was on his way to Kabul around midday.

Elsewhere, three Afghan army soldiers were killed Thursday when their vehicle hit a roadside bomb in eastern Paktia province, said Azizuddin Wardak, the provincial police chief.

Five soldiers were wounded in the blast, Wardak said.