Defense Secretary Ash Carter has landed in Afghanistan to assess the fragile security situation amid reports of increased violence.

Carter's visit comes as his top commander there, Gen. John Campbell, voiced concerns that foreign fighters from Syria and Iraq are joining with Afghans who have declared loyalty to the Islamic State in the east, near the Pakistan border.

Officials have been warning for some time that the presence of IS is attracting disaffected members of the Taliban. Fueling those concerns is a Pentagon report saying that the Taliban has been emboldened by the reduced U.S. military presence in Afghanistan and attacks increased this year.

Carter is planning to meet with his military commanders and troops. He is on a weeklong visit to the region, and spent the last two days in Iraq.