Suspected Taliban (search ) militants on Wednesday ambushed and shot to death five Afghans working on a U.S.-funded project to help end opium farming in the south of the country, officials said.

A man claiming to have kidnapped an Italian aid worker in the Afghan capital threatened Wednesday in an interview on local television to kill her unless his demands were immediately met.

Also, a former foreign minister for Afghanistan's ousted Taliban regime said he would be a candidate in the country's upcoming parliamentary elections.

The workers were ambushed as they drove through Helmand province (search ), about 110 miles northwest of Kandahar, senior provincial official Ghulam Muhiddin said.

Two of the victims were engineers working for Washington-based Chemonics International Inc. (search) and one was a government engineer. The other two were the driver and a policeman employed as a security guard, he said. There were no survivors in the car.

"Police are investigating the killings and are searching for the Taliban attackers," Muhiddin said.

Carol Yee, a senior Chemonics worker in the area, confirmed the killings. She said the men were working on a project to provide alternative livelihoods to farmers growing opium, the raw material for heroin.

Yee said no threats had been made against Chemonics, a global consulting firm that works under contract to the U.S. Agency for International Development (search) and other aid donors.

The United States and other countries are pumping hundreds of millions of dollars into Afghanistan in a bid to crack down on the burgeoning drug trade.

Afghanistan last year produced nearly 90 percent of the world's opium, sparking warnings it is fast becoming a dangerous "narco-state" less than four years after the end of its role as a haven for Al Qaeda (search).

Efforts to eradicate opium crops and raid heroin laboratories this year have sometimes triggered a violent response from drug producers.

However, aid workers have been targeted many times before by Taliban-led militants in the south and east of the country as part of a drive to undermine recovery under the U.S.-backed government that replaced the hardline militia.

Meanwhile, a man who claimed to be holding Italian hostage Clementina Cantoni threatened to kill her unless his demands were met by Wednesday night.

"If our demands are not accepted ... we will show our reaction and finish her," the man, who called himself Temur Shah, told private Afghan Tolo television station in a telephone interview.

Shah did not give any proof that he was holding her.

Cantoni, 32, has been in Afghanistan since 2002 and was working for CARE International (search) on a project helping Afghan widows and their families.

CARE's Afghanistan director, Paul Barker, said the aid group has negotiated with the man who claims to be holding Cantoni.

"The guy, if he is who we think he is, has blood on his hand from previous incidents," Barker said.

The man demanded the government set up more Islamic boarding schools in Afghanistan and provide "alternative livelihoods" for farmers being forced to stop growing opium, and he insisted that independent radio station Arman stop broadcasting a program about young people's social issues. He did not say why he opposed the show.

Shah said Cantoni's health was "very critical," adding that she was bleeding internally and vomiting, and had not eaten in three days. He said she hurt her head while being dragged out of her car Monday.

Authorities have said they suspect Cantoni was kidnapped by the same criminal gang accused of abducting three U.N. workers last year. They were released a month later.

The Italian government said Tuesday that contact had been made with the kidnappers and that Cantoni was unhurt.

Her kidnapping was the latest in a string of attacks targeting foreigners in Kabul, reinforcing fears that militants or criminals are copying tactics used in Iraq.

The Afghan government recently has reached out to members of the Taliban to lay down their weapons and rejoin civil society.

A former member of the Taliban regime announced Wednesday he would run in the upcoming parliamentary elections.

Former Taliban Foreign Minister Wakil Ahmed Muttawakil (search), who is considered a relative moderate, surrendered to U.S. forces in the southern city of Kandahar in 2003 and was held by the U.S. military at its main base in Bagram, north of Kabul. He was freed recently.

"I have the right to be an independent candidate," he told The Associated Press in a telephone interview. "I am doing this for the sake of the people of Afghanistan. If I win, I will work for the peace and development of Afghanistan."

Muttawakil said he registered as a candidate in Kandahar and would compete to represent the former Taliban stronghold in the new 249-seat legislature.