A suicide blast killed 10 persons and injured 40 others on Sunday in Khost city, capital of Khost province in eastern Afghanistan, Gul Mohammadin, head of Khost hospital, told Xinhua.
Four of the injured were in serious condition, Mohammadin said, adding the casualties may rise as the explosion was very powerful.
The blast occurred in the north of the city at around 11:00 a.m. (0630 GMT), he said.
Witnesses said a suicide bomber camouflaged in a police uniform driving a motorbike came close to some policemen and blew himself up.
It was not immediately known how many policemen were killed, while witnesses said most casualties were civilians.
This attack took place only two hours after another explosion killed at least one civilian and injured seven others in a market of the same city.
No one has claimed responsibility for the two blasts.
Khost has been a hotbed of Taliban and other anti-government militants, who clash with Afghan and foreign troops frequently.
Due to rising Taliban-linked insurgency, over 900 persons, mostly Taliban militants, have been killed in Afghanistan this year.