"Our police engaged the enemy with bravery and killed 20 Taliban," he said, adding that three policemen were also injured during the fighting in the Dasht-i-Bakwa area. Officials say insurgents have infiltrated Farah province bordering Iran after being defeated by foreign and Afghan troops in the troubled southern provinces last year.
Separately, US-led troops and aircraft attacked a group of militants preparing to launch a rocket attack in the eastern province of Paktika and killed up to seven rebels on Friday, the coalition forces spokesman said in a statement.
The attack happened in Bermel district, a township on the Pakistani border. "Coalition forces spotted a group setting up rockets and engaged the group with indirect fire. Coalition aircraft dropped two munitions on the site and then another one on five personnel moving into a Wadi (valley)," it said.
"A ground patrol moved to the site and confirmed that two were killed and another five are suspected dead," the statement said. A militant was killed and another was injured late Thursday when a bomb they were planting on a roadside went off prematurely in eastern Kunar province, a police official said.
The injured man was detained by US-led troops for questioning, the official told AFP on condition of anonymity.
The fundamentalist Taliban have waged a bloody insurgency in Afghanistan since they were toppled from power in US-led offensive. The violence claimed more than 4,000 lives in 2006, the worst year since the invasion.