An unmanned spy blimp floating high above the city of Kandahar is being praised by military officials as a useful security tool, but criticized by Afghan locals who say it violates their privacy.

A blimp equipped with powerful spy cameras has been patrolling the skies over Kandahar since June. (Photo courtesy U.S. army)

Known as the "persistent threat detection system" by the U.S. air force, the device is a small blimp outfitted with cameras and microphones that can stream video and audio in real time from trouble spots in and around Kandahar.

Anchored by a tether and capable of being deployed to an altitude of more than 1,600 metres, it is believed to be out of the range of small-arms fire. It's been in use since June and no one has managed to take it down yet, but local residents are threatening to shoot down the blimp over concerns it violates their privacy.

"We are happy for the increased security. But many people here still don't like it," a local resident said when approached by a journalist in Kandahar.

"It has a camera that can see 360 degrees," U.S. air force Col. Marilyn Jenkins says in an army video about the device. "With that camera we can go anywhere in the city and look for any threat or any intentions from the insurgency."

More troubling than the general privacy issues are residents' concerns that the device could be used to spy on women.

Women's rights are a highly contentious issue in Afghanistan, a Muslim country. Earlier this year, a prominent women's rights activist was gunned down in Kandahar, and Afghan President Hamid Karzai drew international condemnation recently for a law that critics alleged legalized rape within Afghan marriages.

"The balloon is for security. This is good," a Pashtun man said. "But we are a tribal people, Pashtun people, and if they can see our women, this is not good."

Pleased with the results thus far, the U.S. military is forging ahead. Plans are underway for similar surveillance devices in Kabul and throughout the country.

The blimp is the latest instance of the U.S. military using balloons in military applications. As far back as the U.S. Civil War, union soldiers used hot air balloons as surveillance platforms.