Fayaz Aziz / Reuters

A driver who survived a shooting by unidentified gunmen in Swabi arrives at a Peshawar hospital on Tuesday after gunmen ambushed the car filled with aid workers that he was driving.

Updated at 10:20 a.m. ET: PESHAWAR, Pakistan -- Motorcycle-riding gunmen shot and killed seven aid workers Tuesday in an ambush near a toll plaza in the Swabi district of Pakistan's northwest Khyber Pakhtunkhwa province.

Police said the gunmen rode their motorcycles in front of a van carrying the aid workers in order to stop it before opening fire on members of the nongovernmental organization Support With Working Solutions (SWSS). Six women and one man were shot dead at the scene, District Police Chief Abdur Rasheed Khan said, adding that the van's driver was seriously wounded.

The six women were serving as social workers and the man, a physician, was providing community health services, said Javed Akhtar, chief executive of Support With Working Solutions. They had just come from a meeting at a community center run by the organization.

Khan said the bodies of the victims were taken to the regional Shah Mansoor Hospital in Swabi.

Threats
He noted that NGO workers, particularly women, had been receiving threats from unknown people.

From alcohol to kites: An A to Z guide to the Islamic Republic of 'Banistan'

Akhtar said his organization, which receives funding from the United Nations and the Pakistan Poverty Alleviation Fund, has for now halted its work.

"We suspended our services due to threats to our staff members," Akhtar said. "We have 160 staff members, most of them females, working with the government in health education in underdeveloped areas of the country."

More news about Pakistan on NBCNews.com

Akhtar said the group has been working in Swabi for two years but had never previously felt serious dangers.

“We are working since 1992 in Pakistan and set up our services in Swabi two years ago, but we never faced any such threat, as all our staff was local," he said, adding, "This seemed to be part of a campaign against the polio drive."

Slideshow: Pakistan: A nation in turmoil

Muhammed Muheisen / AP

Images of daily life, political pursuits, religious rites and deadly violence.

Launch slideshow

Last month, gunmen killed nine health workers taking part in a national polio vaccination drive in a series of attacks. Most of the victims were young women earning about $2 a day.

The Taliban said it did not carry out those attacks, although its leaders have repeatedly denounced the vaccination program as a plot to sterilize people or spy on Muslims.

Complete World coverage on NBCNews.com

Aid workers have frequently been kidnapped or killed in Pakistan, a nation of 180 million that is struggling to contain a Taliban insurgency and plagued by endemic corruption and violent crime.

Reuters contributed to this report.

More world stories from NBC News:

• World marks 2013 with fireworks, fanfare and -- for some -- new freedoms
• Beer now considered alcohol, not food, in Russia as new restrictions take hold
• From alcohol to kites: An A to Z guide to the Islamic Republic of 'Banistan'
• Photoblog: With the motherland close at heart, Russian culture lives on in Israel
• Photoblog: Reuters cameraman wounded by Syrian sniper
• Body of India rape victim cremated in New Delhi

Follow World News from NBCNews.com on Twitter and Facebook