Pakistani troops repulsed an attack by dozens of armed Taliban militants on a checkpoint close to the Afghan border on Wednesday in fighting that killed six soldiers and at least 20 insurgents, the armed forces said.

Pakistan has carried out a series of operations in the border region over the last 18 months, but the militants have proved resilient foes. The U.S. has pushed Islamabad to keep up its offensives, arguing that militants on its side of the border are involved in attacks on American and NATO troops in Afghanistan.

Wednesday’s attack by up to 100 militants occurred in the Bara area of Khyber, a tribal region home to a top supply route for troops across the border.

A statement from Pakistan’s paramilitary Frontier Corps said the attackers used several suicide car bombs, but that soldiers fought back, destroying the vehicles during the clash. At least 15 soldiers also were wounded in the attack, the statement said.

There were conflicting accounts about how many militants were killed. The Frontier Corp said 25 insurgents died, but the army put the number at “about 20.” An additional 30 militants were wounded, the army said in a statement.

The information is nearly impossible to verify independently. Access to Khyber and other tribal regions is restricted, and the border area as a whole is remote and dangerous.

Also on Wednesday, at least six alleged insurgents were killed by suspected U.S. missiles in the nearby tribal region of North Waziristan, two Pakistani intelligence officials said.

Two missile attacks one hour apart destroyed an abandoned school near the town of Mir Ali, said the officials, who spoke on condition of anonymity because they were not authorized to speak to media.

The U.S. rarely discusses its missile campaign. Pakistan publicly protests it as a violation of its sovereignty, though it is believed to secretly assist in the strikes.

North Waziristan has been the target of the majority of recent missile attacks. It is home to several militant groups who focus on battling U.S. and NATO forces in Afghanistan.

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