KABUL, Afghanistan — Taliban fighters said on social media that they shot down a U.S. drone this week over Afghanistan's volatile region near the Pakistan border.

Officials with the U.S.-led military operation in Afghanistan confirmed Tuesday that they lost contact with the unmanned aircraft that was flying over the country's Nangahar province. That's an area where Taliban forces have made advances in recent months and where Islamic State militants are believed to have a small presence.

"We can confirm that we have lost contact with a remotely piloted aircraft," officials with Resolute Support, the NATO operation in Afghanistan, said in a statement. "At this time we cannot confirm the cause."

The loss of the drone comes amid increasing U.S. military operations in Afghanistan in an effort to help the Afghan army beat back Taliban fighters who are seeking to tighten their grip on provinces that surround Kabul, the nation's capital.

Also on Tuesday, officials in the country's northeastern Kunduz province reported that a U.S. drone killed 12 Taliban fighters, including one of the insurgent group's senior commanders.

That attack took place Monday in the province's Chahar Dara district, which the Afghan army won back after a bloody battle in April, an official with the Kunduz police said. NATO officials did not immediately confirm that the drone strike took place.

With the possibility of peace negotiations between the Afghan government and Taliban leaders now a distant dream, both sides are vowing to fight more aggressively in the coming weeks.

Taliban leaders crowed over the downed drone on Twitter, and on the group's website.

"The wreckage of the drone is now in Mujahideen possession," the insurgent group said on its Twitter feed, which showed a photo of a busted fuselage lying on a craggy hillside.