A bomb placed on a bicycle and detonated by remote control exploded next to a police bus in Kabul on Tuesday, wounding 11 people, police said.
Insurgents also attacked a police checkpoint in central Wardak province late Monday, leaving one policeman dead and wounding two others, said Jan Mohammad, a provincial police official.
NATO and Afghan troops, meanwhile, clashed with militants in southern Zabul province on Monday. Two insurgents were killed and one Afghan soldier was wounded during the firefight, said Noor Mohammad Paktin, Zabul's police chief.
Police in Kabul picked Tuesday through the twisted remains of the bicycle bomb, which wounded both police and civilians. The windows on the bus were shattered but it was not otherwise heavily damaged, and police drove it away about an hour after the 8 a.m. attack.
"They are targeting police," said Jan Agha, a police officer at the scene. Agha complained that his US$50 monthly salary was not worth the increasing risks that police are facing.
Militants have been stepping up attacks, including roadside and homicide bombings, across Afghanistan the last several months. Foreign troops and Afghan security forces are the most frequent targets.
"I just heard an explosion and saw a big plume of smoke," said Barat Noori, who works in a nearby bakery. He helped the injured policemen and civilians into taxis that took them to the hospital.
A homicide bomber killed 12 people and injured 40 late last month outside the gates of the Interior Ministry, which oversees the country's police force.