A bomb attack in the western Afghan city of Herat has killed at least 12 people and injured at least 20, police officials say.
They said the attack had targeted a police convoy, killing and wounding both police and civilians.
Insurgent attacks on security forces have increased in the run-up to the presidential election on 20 August.
However, attacks have been mainly in the south and east, where Taliban rebels have their strongest presence.
Police spokesman Raouf Ahmedi said the explosion on Monday in Herat was detonated by remote control, AP reported.
Another police official, Esmatullah Alizai, told journalists that the bomb had been left in a roadside rubbish bin.
"It exploded as the convoy of district police passed by," he said.
He was also quoted as saying that two police officials, a woman and child were among those killed, and that the district police chief had been seriously injured.
Gateway to Iran
The BBC's David Loyn, in the Afghan capital, Kabul, says the target may have been the governor of a district of Herat province, thought to have been travelling in the convoy.
A reporter for the AFP news agency saw several police vehicles and private taxis damaged by the blast.
Motorcycles and bicycles were strewn over the site, while children's shoes and a woman's veil had been abandoned there, he said.
Our correspondent notes that Herat has been relatively peaceful in recent weeks as insurgents have stepped up attacks elsewhere in Afghanistan.
Herat is enormously important to Afghanistan as the gateway to Iran and the town where most of the legitimate customs revenue for the Afghan government comes from, he adds.
The bombing comes after the Taliban explicitly threatened to disrupt the upcoming election.
A series of attacks on foreign forces at the weekend killed nine soldiers, continuing an increase seen in July, which was the deadliest month for foreign soldiers since they arrived in the country in 2001.
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