The commander of U.S. forces in Afghanistan says affiliates of the Islamic State group are attempting to establish a regional base in the eastern city of Jalalabad.

U.S. Army General John Campbell says "foreign fighters" from Syria and Iraq have joined Afghans who have declared loyalty to IS in the eastern province of Nangarhar, bordering Pakistan.

In an interview with The Associated Press on Tuesday, he said "there are indications" they are trying to consolidate links with the group's leadership in Syria and Iraq.

The Islamic State group controls large regions of Iraq and Syria. Fighters loyal to the group in Afghanistan include disaffected Afghan and Pakistani Taliban who have battled with the Taliban in recent months.

Afghan and Western officials say IS affiliates control a number of border districts.