A Palestinian man in the West Bank town of al-Ram was arrested early Monday after a M-16 rifle was found during a raid of his home, police said.
During the raid, officers also seized ammunition, magazines and other illicit materials.
Police said the 24-year-old suspect was taken for questioning after his arrest.
Separately, security forces arrested another 20 suspects in the West Bank during overnight raids.
The army said the suspects were wanted for involvement in terrorism and violent rioting against security forces and Israeli civilians.
During the raids, security forces seized three guns, including the M16 found in al-Ram, according to the army.
The suspects were taken in for questioning following their arrests, the army said.