Seven U.S. military trainers were wounded on Sunday when protesters in Kunduz in northern Afghanistan threw a grenade at their base, provincial police chief Samihullah Qatra told reporters.

NATO's International Security Assistance Force (ISAF) confirmed there had been an explosion outside one of its bases in northern Afghanistan, but declined to comment on casualties.

(Reporting by Fraidoon Elhaam in Kunduz, Amie Ferris-Rotman in Kabul; Editing by Michael Georgy)