NATO forces, backed by punishing airstrikes, have clawed back volatile southern Afghan regions from Taliban insurgents during a large-scale campaign that has killed at least 510 suspected militants, the alliance said.

Security forces also killed a dozen Taliban on Tuesday and detained more than 30 in raids aimed at quelling a rampant insurgency.

CountryWatch: Afghanistan

Highlighting the instability, police said gunmen kidnapped a Colombian aid worker and two Afghan colleagues on Sunday in a remote mountain region west of Kabul.

It was not clear who kidnapped the men, but Taliban militants have been fanning Afghanistan's deadliest period of bloodshed since their hard-line regime was toppled by U.S.-led forces in late 2001 for hosting Usama bin Laden.

In southern Kandahar province, thousands of NATO and Afghan forces, backed by intense daily U.S.-led airstrikes, have killed at least 510 suspected Taliban in a campaign dubbed Operation Medusa, that began Sept. 2.

Purported Taliban spokesmen reject the death tolls as exaggerated. Journalists have been unable to enter the region because of the ongoing campaign.

On Tuesday, NATO said its forces had taken back control of 65 percent of "contested areas" in Kandahar's neighboring Zhari and Panjwayi districts.

Up to 1,500 families have been displaced by the violence, alliance spokesman Maj. Scott Lundy said.

Footage purportedly taken by the Taliban showed a crater which the group claimed was a civilian house hit by an airstrike.

Canadian Brig. Gen. David Fraser, commander of NATO forces in southern Afghanistan, accused Taliban militants of sheltering in residential areas during the operation.

In Kabul, a top American general said violence has increased in the south because of efforts by Afghan and foreign forces to wipe out the Taliban.

"Five years ago, the Afghan National Army was zero," Maj. Gen. Robert Durbin, who heads the training of Afghan soldiers and police, told CNN. "We now have sufficient forces, that's why there is some tough fighting down in Kandahar."

A fierce gunbattle broke out in Ghazni province, south of Kabul, as Afghan soldiers and police, backed by U.S.-led coalition forces, battled insurgents in mountainous Andar district, a provincial official said.

Twelve militants were killed in the clash, the official said.

The Colombian aid worker, his Afghan translator and a driver for a French Foreign Ministry-funded Aid Mission for the Development of Rural Economies in Afghanistan, were kidnapped in Wardak province's Jalrez district, a police official said.

In Paris, French diplomats confirmed the kidnappings, but provided no further details. Colombian officials had no immediate comment.

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