Afghan officials said Taliban fighters in the southern Afghan province of Helmand attacked a police checkpoint early on Tuesday, killing 12 police officers and stealing weapons and ammunition.
A provincial official added that it could be an insider attack as one of the guards was still missing.
"An investigation is ongoing to find out if someone from inside has defected to the Taliban and paved the way for this crime," the official said.
"The Taliban attacked a guard with silenced guns and then entered the check post," Helmand deputy police chief Haji Gulai told reporters.
They attacked other policemen with hand grenades and killed all of them. They later took their weapons and ammunition and escaped.
In a separate incident, another 12 policemen were killed in the Marjah district of Helmand after an hour-long gun battle, Taliban spokesman Zabihullah Mujahid said.
Taliban fighters now control most of Helmand, where British and US forces suffered their heaviest casualties of the war in years of fighting following the ouster of the Taliban in 2001.
Afghan security forces now control less than 60 percent of the country, according to US estimates. The Taliban control about 10 percent and the remainder is contested between government and insurgent forces.