A bomb hidden in a trash can tore through a crowded street near a police convoy in the western Afghan city of Herat Monday, killing 12 people.
Afghan officials say the blast also wounded some 30 people, including the police chief of the nearby Injil district, who is in critical condition.
A Taliban spokesman claimed responsibility for the attack, saying police commander Mohammad Issa was the intended target.
Taliban militants have increased their attacks across Afghanistan ahead of the August 20 presidential and local elections. The group urged Afghans to boycott the polls and ordered its fighters to block roads to prevent people from voting.
The new NATO chief, Anders Fogh Rasmussen, said Monday in Brussels that the alliance needs more international help in Afghanistan to prevent it from "becoming again the center of international terrorism."
On Sunday, the top U.N. envoy in Afghanistan, Kai Eide, called for peace talks with top Taliban leadership to end the country's conflict.
The Taliban's leader, Mullah Omar, has rejected offers for dialogue, saying no talks can take place until all foreign troops are out of the country.
At least nine coalition troops, six Americans, two Canadians and one French, were killed in the first two days of August, while militants also have stepped up attacks on election candidates and their staff ahead of the election.
Some information for this report was provided by AFP, AP and Reuters.