Iqbal Khaibar, a PPM leader, said the activists were kidnapped in the Bala Buluk district of Farah Province while traveling from the neighboring province of Herat.
Dadullah Qani, a member of the Farah provincial council, confirmed the incident.
Farah police said efforts have begun to track the kidnappers.
There was no immediate comment from the Taliban.
The activists were in the middle of a fresh round of rallies, traveling around the country to spread a message of peace and urging all sides of the conflict in Afghanistan to agree upon a cease-fire, the PPM said in a statement.
The group said this is the fourth time the Taliban has abducted PPM peace marchers.
The most recent incident was in June, when the Taliban held 25 peace activists who traveled to the Taliban stronghold of Musa Qala in Helmand Province in an attempt to meet with the militants and plead with them to seek peace. They were released several days later.
The PPM attracted international attention last year with its peace marches across Afghanistan and in Kabul during which they warned about the record levels of violence across the country.
The movement has always claimed to be an impartial movement, only advocating for peace in the war-torn country.