A wounded Afghan policeman receives treatment at a hospital in Kandahar after a powerful homemade bomb killed eight police officers and three detainees, the second of two attacks in on Saturday. (Jangir/AFP/Getty Images)

At least 18 Afghan police officers were killed in two separate explosions Saturday in Afghanistan, officials said Sunday, one of the bloodiest days in months for the force charged with the country’s security once Western troops leave.

In the first attack, a suicide bomber targeted a group of police officers in northern Kunduz province. Ten officers, including the city’s counter-terrorism chief, were killed.

A spokesman for Taliban-led insurgents said the strike was carried out by a member of the group.

The second incident happened hours later in the former stronghold of militants in southern Kandahar, a spokesman for the provincial governor said. Eight police officers and two suspected insurgents they had detained were killed when the vehicle they were traveling in struck a roadside bomb.

Six more officers were wounded, and a third suspected insurgent survived the blast, said Javid Faisal, a spokesman for the governor. The explosion happened after police discovered a mine in another section of the city and detained three men on suspicion of planting the device, he said.

No group has claimed responsibility for the second blast, but the Taliban relies on roadside bombs in its campaign against foreign and Afghan forces.

The loss of 18 police officers in one day is a big one for Afghan forces, who have been taking on a growing role from NATO and U.S. troops as part of a transition that will see the American mission in the country formally end in 2014.

Afghan forces say they have sufficient numbers to block the return of the Taliban to power, but have been pushing Western troops to provide them with air power and heavy weapons.