Michael Leighton Phillips, 24, a volunteer and a student, was teaching English for Project Hope in Palestinian refugee camps near the West Bank city of Nablus when he was kidnapped.
Phillips was abducted by a previously unknown militant group calling itself Ansar A-Sunna, YnetNews.com reported. However, a Palestinian official later pointed the finger at the Popular Resistance Committees, Ynet said.
The al-Aqsa Martyrs' Brigades are a Palestinian militant group closely linked to the Fatah political party of Palestinian President Mahmoud Abbas.
A senior al-Aqsa official who participated in the raid told Ynet Phillips was held for 24 hours and was found tied up in the Nablus apartment.