Afghan officials say at least 27 people were killed when a suicide bomber detonated explosives in a crowded area in southern Helmand province.
At least 45 other people were wounded.
NATO officials say the bomber was driving a motorized rickshaw when he blew himself up next to a bus station.
An Afghan Defense Ministry spokesman, General Mohammad Zahir Azimi, says a local police commander who survived the attack appeared to have been the target of the blast, which killed 13 other policemen.
The explosion in the town of Gereshk, in Helmand province, is considered one of the deadliest in Afghanistan this year.
NATO says that Afghan security forces have been deployed to secure the area around the site of the attack.
Some information for this report was provided by AFP, AP and Reuters.