On Wednesday, a vehicle bomb in Helmand province killed at least two policemen.
Taliban fighters on Monday briefly took control of the administrative building of Farah's Anar Dara district, killing eight police, before they were beaten back by security forces, officials said.
The Taliban 's muted response to Afghan President Ashraf Ghani's offer of peace talks last month reflects an internal debate over the merits of engaging with a government that the group has long viewed as illegitimate, analysts say.
Farah provincial council member Abdul Samad Salehi said the security forces were battling the Taliban on three fronts.
Other council members said the assault lasted for three hours.
Elsewhere in Afghanistan, a suicide truck bomb struck a checkpoint in the southern Helmand province, killing at least two border police, according to General Abdul Ghafar Safi, the police chief of the province, which borders Pakistan.
The defense secretary emphasized that the recent peace offer does not eliminate the need for offensive operations against the Taliban, she said, and noted the importance of continued progress by Afghan forces on the battlefield.
But Afghan President Ashraf Ghani offered talks without preconditions with the Taliban insurgents last month, in what was seen by US officials as a major overture from Kabul.
The Western-backed government in Kabul has been struggling to fend off the Taliban and other militant groups since the withdrawal of most North Atlantic Treaty Organisation troops in 2014. That would be a bridge too far.
The Taliban's policy on whether or not to accept peace talks with Afghanistan's government has been thrown into doubt by an editorial published on the group's website.
Western diplomats and officials in Kabul say contacts involving intermediaries have been underway with the aim of agreeing on ground rules and potential areas of discussion for possible talks with at least some elements in the Taliban.
Asked whether the United States would be willing to talk directly with the Taliban, Mattis reiterated the USA position that the talks should be led by Kabul.
The United States has refused to withdraw troops as demanded by the Taliban and has insisted that the Afghan government must play a lead role in peace negotiations.