PESHAWAR, Pakistan (Reuters) -- Pakistani government forces have killed 52 Islamist militants to the south of the Khyber region, the site of a vital supply route for Western forces in Afghanistan.
Islamist militants have stepped up attacks on the road into land-locked Afghanistan since last year, exposing the vulnerability of Western supply links just as the United States is planning a surge of troops to tackle the Taliban.
Army helicopter gunships attacked the militants near the border between the Khyber and Orakzai regions on February 6, said Tariq Hayat, Khyber's top administration official.
"Fifty-two militants were killed and a huge ammunition depot and eight vehicles were destroyed," Hayat told Reuters.
"Most of the deaths occurred because the destruction of the ammunition depot triggered a series of explosions," he said.
There was no independent verification of the casualty figure that Hayat said came from the helicopter pilots and air surveillance.
Security has deteriorated sharply in northwestern Pakistan along the Afghan border including in the Khyber region since last year.
Earlier, a suicide car bomber blew himself up and wounded seven people when police stopped him at a checkpoint on a small bridge on the road through the Khyber Pass.
The blast damaged the bridge and a truck waiting to cross it but administration official Fida Bangash said he suspected the bomber was heading to a bigger bridge destroyed in a blast on February 3 that soldiers are repairing.
"The bomber was probably heading toward where army engineers are fixing the bridge destroyed on Tuesday," Bangash said.
Traffic on the road was suspended for two days after the February 3 attack on the 30-meter iron bridge, 23 kilometers west of the city of Peshawar.
But soldiers have cleared a detour over a dried-up river and trucks have resumed taking supplies up to the border.
The U.S. Defense Department says the U.S. military sends 75 percent of supplies for the Afghan war through or over Pakistan, including 40 percent of the fuel for its troops.
Escalating violence in nuclear-armed Pakistan has raised concerns about the stability of a country seen as vital to efforts to stabilize Afghanistan and defeat al Qaeda.
The violence has also eroded investor confidence, which in turn has contributed to economic difficulties that forced the country into a $7.6 billion International Monetary Fund loan agreement in November.
Security has also deteriorated sharply in the Swat valley, northwest of Islamabad, where troops are struggling to stem spreading Taliban influence.
But the violence has not been confined to the northwest, and militants have set off bombs in all of Pakistan's main cities over the past year.
Police said 27 people were killed on the evening of February 5 in a suspected sectarian attack outside a Shi'ite Muslim mosque in the town of Dera Ghazi Khan in the center of the country.
Angry Shi'ite protesters ran riot in the town the following day, burning a police station, ransacking a Sunni Muslim religious school, and blocking roads in the town.
Sunni Muslim militants linked to Al-Qaeda have been blamed for a series of attacks on minority Shi'ite Muslims in recent years. About 80 percent of Pakistanis are Sunni Muslim.