Separately, a suicide car bomber blew himself up Sunday near an Afghan army convoy in eastern Laghman province, killing five civilians, police said.
The three men from the southern province of Helmand were arrested and allegedly "confessed to their crime" of being spies for NATO and the Afghan government, said Mullah Abdul Qasim, a Taliban commander in the north of Helmand. Qasim said information from the three men led to the deaths of two Taliban commanders.
A villager from Musa Qala, Namatullah Khan, said the lifeless body of one of the men hung from the town's main street for three hours before villagers took him down and buried the corpse.
"The Taliban told the other people of Musa Qala that whoever gives information to the government and our enemies will be punished in the same way as this informer," Khan said.
Another man was hanged from a tree near a bridge by the town of Gereshk, and the third was executed in between Gereshk and Musa Qala, said Naeem Shah, a resident of Gereshk, where the two bodies were later taken.
NATO last month launched its largest ever military operation to root out militants in the northern part of Helmand, the world's leading opium-producing region.
In eastern Afghanistan, a suicide car bomb targeted an Afghan army convoy near Laghman province's city of Mihtarlam, killing five civilians, including three children, said provincial police chief Abdul Karim. Another civilian and five soldiers were wounded, he said.
The soldiers were on their way back to base after helping flood victims in the area, said Defense Ministry spokesman Zahir Azimi.
Azimi gave a different casualty count, saying three civilians were killed, and five civilians and eight soldiers were wounded. The differing tolls could not immediately be reconciled.
In southern Kandahar province, suspected Taliban insurgents ambushed two convoys of Afghan police, killing seven policemen and wounding four, an official said Sunday.
Taliban ambushed one convoy patrolling Saturday night in the border area between Spin Boldak and Shorawak districts, said Kandahar provincial police chief Esmatullah Alizai. One policeman was injured in the ensuing clash, he said.
A second police convoy coming to help the first was also ambushed, and seven policemen were killed and three others wounded, Alizai said.