The deaths are the latest in a spate of killings targeting Afghan government figures and others aligned with international forces.
In other violent incidents, two Italian soldiers were killed and two others seriously wounded when their convoy struck a roadside bomb in northern Afghanistan, the Italian army said on Monday.
The convoy hit the bomb while on its way from the western city of Herat to Bala Murghab, the army said.
The attack follows the death of two Nato soldiers on Sunday in southern Afghanistan. One of the soldiers was American, officials said, but have not disclosed the nationality of the other dead man.
So far this month, 27 Nato troops, including 16 US soldiers, have been killed across Afghanistan, many in the south where Nato forces are moving in as part of a stepped-up security operation in Kandahar.
Late on Sunday, in Kandahar city, a suicide bomber detonated his cache of explosives near the gate of an Afghan border police residence.
Sher Mohammed Zazai, the Kandahar police chief, said at least three people were wounded in the attack, which occurred in the city's northeast.
"There was a suicide attacker on a motorbike who blew himself up when he got near the gate," he said.
Zelmai Ayubi, spokesman for the governor of Kandahar, said at least four border policemen were injured.
He said two other suicide attackers entered the police compound, but were shot dead by police during a gun battle before they could detonate their vests of explosives.
Earlier on Sunday, two attackers on a motorbike opened fire in Kandahar on a car belonging to an intelligence official who was on his way to work, Zazai said.
The intelligence official's driver was killed.