The judge, an intelligence official and an employee in Helmand province's education department were killed as they returned home from a dinner in the Nad Ali district to Lashkar Gah, the capital of Helmand.
"As they were coming from a dinner party, they were ambushed and killed on their way back to Lashkar Gah," provincial security chief Amanullah told AFP.
"It was the the work of the enemies of Afghanistan - Taliban and their terrorist allies," he added.
Police chief executed
Taliban members claimed on Sunday to have executed a district police chief, who was among 13 hostages seized in a raid on a district government headquarters in southern Afghanistan, a Taliban spokesman said.
Nanai Khan, police chief of Kandahar province's Mian Nishin district, was shot three times on the orders of Taliban religious leaders, the group’s spokesman Abdul Latif Hakimi said on Sunday.
"At 8.30 this morning, we executed Nanai Khan after a fatwa from the mullahs," he said. "They said his crime was high so he should be executed."
Hakimi said the officer's body had been dumped at a village in Mian Nishin named Shai Khan. "The government can come and pick up his body," he said.
Hakimi said the 30 others being held, including the chief of the district, were still alive. "Their trial is going on."
A senior police officer in Kandahar confirmed on Saturday that the main government building in Mian Nishin, capital of the district of the same name, was under Taliban control after attacks on Thursday and Friday night in which 30 police officers and the district chief were captured.
General Salim Khan, the deputy provincial police chief, said he had no information as to the fate of those being held. He said 13 people had been captured in all.
The capture of the officers is a
new crisis for the authorities
The capture of the men is a fresh crisis for authorities in Kandahar, the worst-hit province in a surge of violence in recent months that has raised fears for parliamentary elections, due on 16 September.
Taliban commander Mullah Rahim, who led the attacks, telephoned Reuters on Saturday night and handed the phone to Nanai Khan, who said he was going to be put on trial.
Asked if any of the group had been killed, a clearly nervous Khan initially replied: "Yes." But after a few seconds of silence on the line, he corrected himself and replied: "No, no."
The district is in the north of Kandahar province about 400km southwest of Kabul and was the scene of joint operations by Afghan and US-led forces early this week in which government officials said nine guerrillas were killed.
Meanwhile, AFP has reported that Taliban guerrillas fired at least three rockets, one of them near a US military outpost, into Afghanistan's southern city of Kandahar early on Sunday, but no one was hurt.
One landed near the former home of the Taliban's fugitive leader Mullah Omar, said General Salim Khan.
The home is currently used by US special forces.
The two other rockets exploded around the city but caused no damage, Khan said.
He blamed the attack on remnants of the fundamentalist militia, which ruled the country until it was ousted by US-led attacks in late 2001. The guerrillas have stepped up attacks on US and government targets over recent months.
"The rockets were fired by the Taliban"
General Salim Khan,
deputy chief of police
"The rockets were fired by the Taliban," the commander told AFP.
Kandahar, the Taliban's former power base, has been hit by a wave of renewed insurgency, with militants staging attacks and bombings over the past month.