Gen. Abdul Wahab Walizada, the Afghan army's Western corps commander, said police had left Farah province's small Bakwa town Monday, but would not say whether Taliban militants active in the area had taken control.
Baryalaj Khan, spokesman for the Farah police chief, said they had lost contact with police in Bakwa. It wasn't immediately known if they were forced out or just fled.
The retreat followed Sunday's bombing of a car carrying the province's police chief on his return from destroying poppy fields. The police chief was unharmed, but four other officers in the vehicle were killed and two wounded.
Khan blamed Taliban militants for the attack, saying they were involved in the drug trade, but gave no evidence to support his claim. Bakwa lies about 40 miles from Afghanistan's biggest opium-producing province of Helmand.
Taliban militants overran Helmand's town of Musa Qala on Feb. 1, defying a peace deal between the government and elders last fall that capped weeks of fighting. The pact was supposed to bar both Taliban fighters and NATO soldiers from coming within three miles of the town center.
Thousands of residents have fled the area since the Taliban seized Musa Qala, fearing a NATO attack and renewed clashes with the militants. The government is negotiating with elders to get them to persuade the militants to leave.
NATO-led troops have a small presence in Farah province, but alliance officials in Kabul referred all questions on Monday's retreat to the Ministry of Interior. Officials there could not reached for comment.
In Ghor province, meanwhile, a clash between poppy farmers and police conducting eradication left one civilian dead and two wounded, said deputy provincial governor Kramuddin Rezazada.
Some 500 people had gathered to protest government attempts at poppy eradication following last year's record crop.
Afghanistan is the world's largest producer of opium poppy. In 2006, production in the country rose 49 percent to 6,700 tons — enough to make about 670 tons of heroin.
The government rejected U.S. offers of ground-spraying and pledged it would step up poppy eradication using tractors and manpower.
In southern Afghanistan, suspected insurgents fired a rocket at a Canadian military's armored vehicle in the city of Kandahar on Sunday, but no troops were injured in the attack, said Capt. Alex Watsen, a spokesman for the force.
Canadians fired back, killing one suspected militant, Watsen said. One policeman also was killed in the ensuing gunfight, he said.