The blast took place after a police vehicle running along a road in Mehar Abad locality of provincial capital Tirin Khot was struck by a roadside planted bomb, deputy provincial police chief Mohammad Islam Kochai told Xinhua.
The injured were shifted to a hospital, he said, blaming Taliban insurgent group for initiating the blast which occurred at around 3:30 p.m. local time.
The police Ranger vehicle was also destroyed in the explosion, he added.
The Taliban has intensified attacks over the past couple of months as the Afghan National Security Forces (ANSF) assumed the full security charges from NATO-led troops after a four-year security transition.
Earlier on the day, two militants were seriously wounded after a bomb they were planting in Kunduz city, the provincial capital of northern Kunduz province went off accidentally, according to provincial police spokesman Sayyed Sarwar Hussainee.
On Jan. 1 this year, the U.S. and NATO-led troops switched from combat to support role -- NATO-led Resolute Support mission, which will focus on training, advising and assisting Afghan forces, and nearly 13,000 foreign forces will be involved in the mission, according to NATO officials.