US-led forces and Afghan troops have killed scores of Taleban fighters in the western province of Herat, a coalition statement says.
Nato says it is taking the fight to the militants
It said 87 had been killed in a 14-hour battle on Sunday, 49 died two days earlier and one US soldier died.
There is no independent confirmation or word from the Taleban on the deaths. It would be their worst losses this year.
Meanwhile in the southern province of Helmand, UK-led forces have launched a major offensive against the Taleban.
Up to 3,000 Nato-led troops, including Afghans and US forces, are involved in Operation Silicon in the Sangin Valley.
The clashes near Shindand, about 120km (80 miles) south of the city of Herat, are among the bloodiest the province has seen in recent years, reports say.
The troops called in air support which dropped "multiple munitions on several identified enemy locations".
Herat is near the border with Iran and the area has been relatively quiet, compared with the south and east where most violence has taken place.
Analysts say violence in the west of the country may be a result of the Taleban being squeezed by the build-up of foreign troops in the south and east.
BBC security correspondent Rob Watson says the Taleban have tended to avoid direct and large scale confrontations with Nato and US forces so far this year - preferring instead to rely on roadside bombs and suicide attacks.
The coalition statement said US special forces accompanied by police and other coalition members had been patrolling in the Zerkoh valley when they attacked Taleban positions with mortar, small arms and rocket-propelled grenade fire.
"A total of seven enemy positions were destroyed, and 87 Taleban fighters were killed during the 14-hour engagement," the statement said.
It said there had been no civilian casualties reported.
Coalition spokesman Army Major Chris Belcher said Afghan police had taken part, but the Associated Press news agency quoted Shindand district police chief Gen Gul Aqa denying that Afghan police and army had been involved.
"The Americans carried out an independent operation in the Zerkoh," he said.
AP quoted him as saying a "large number of people" had been killed in the attack, but he did not provide a figure or say who had died.
The police chief spoke as local people gathered in front of the police station and government headquarters in Shindand district chanting "Death to America!".
"The people they have killed are not Taleban, they are civilians. They have killed civilians including children," one local told the AFP news agency by telephone from the area.
Unconfirmed reports say the protestors set fire to the government offices, and police fired shots to disperse the demonstration.
A similar protest took place on Sunday near the eastern city of Jalalabad after at least two civilians were killed in a raid by US-led forces.
In the south, Operation Silicon aims to drive Taleban fighters from their stronghold in the Sangin valley in Helmand province - the biggest poppy-producing area in the world for opium.
It is part of the wider Operation Achilles launched in March to prepare for reconstruction work in the area by the Afghan government.
The BBC's Alastair Leithead, who is with troops in the area, said the fighting has developed into a major battle on several fronts.
Apache helicopters and dozens of British armoured vehicles moved in at first light and heavy fighting went on for hours, he says.
Across Afghanistan, bloodshed has returned to levels not seen since the fall of the Taleban regime in 2001. Some 4,000 people are believed to have died last year in the insurgency - about a quarter of them civilians.
About 30,000 coalition troops and another 10,000 US-led ones have been battling to reduce violence and boost the authority of President Hamid Karzai.
Violence has surged in recent weeks, with the onset of spring.