The massacre was carried out by the Taliban members on Sunday evening in the restive Bala Bulok district, local officials said.
“Taliban members have blown up an army outpost after digging a 400-meter tunnel to access it from a nearby house,” Farah Governor Taj Mohammad Jahid said.
Taliban members, who set fire to the military station after killing the soldiers stationed there, have also captured one soldier.
The Taliban did not immediately claim responsibility for the deadly attack.
Afghanistan has seen a surge in violence as peace talks that started in September between the Taliban and the Afghan government have so far failed to achieve a breakthrough.
The majority of bomb attacks in Kabul in recent months have been sticky bombs, which are explosive devices with magnets attached to vehicles and detonated by remote control or timer.
Since 2001 when the United States invaded Afghanistan, over 100,000 people have been killed in the war, including more than 4,000 ISAF soldiers and civilian contractors, more than 62,000 Afghan national security forces, 31,000 civilians, and even more Taliban members.