AFP - A bomb targeting Afghan police exploded in the heart of Afghanistan's western city of Herat on Monday, killing 12 people and wounding another 20 during rush hour, police said.
The attack heightens concerns that the country's Taliban-led insurgency is spiking less than three weeks before landmark presidential and provincial council elections on August 20.
Provincial police chief Esmatullah Alizai told reporters that the blast was caused by a bomb planted in a roadside rubbish bin.
"It exploded as the convoy of district police passed by," he said.
"Twelve people have been killed in this explosion and 20 other people have been wounded. Among those killed are two police."
Another police officer had said the attack was caused by a suicide bomber.
The blast hit the centre of Herat during the busy morning rush hour and an AFP reporter saw several police vehicles and private taxis damaged.
Motorcycles and bicycles lay discarded at the site, and children's shoes and a woman's veil were left abandoned on the ground, he said.
There was some police gunfire after the blast, the reporter said.
There was no immediate claim of responsibility for the explosion.
The Taliban, the main extremist group in Afghanistan, has carried out multiple bombings as part of an insurgency aimed at winning back power after their 2001 overthrow by the US-led invasion that is now at its deadliest.
The insurgent group has called on Afghans to boycott the elections and ordered its fighters to block all roads a day before polling stations open.
Authorities said Sunday that other insurgent attacks killed three US and two Canadian soldiers, as well as seven Afghan policemen and soldiers.
There are more than 100,000 foreign troops based here helping Karzai's government battle the insurgency.