Palestinian Authority President Mahmoud Abbas has issued a decree banning people from carrying of weapons and explosives without a permit.
Mr Abbas has been under pressure to take firm action against militants
"This measure aims to suppress all unofficial armed groups", the official Wafa news agency reported.
Mr Abbas' effective rule extends to the West Bank only, after Hamas militants seized control of the Gaza Strip.
Correspondents say many Palestinians carry unofficial arms, and it is not clear how the ban will be enforced.
The ban targets Hamas, the main rival of Mr Abbas' own Fatah movement, but also the Al-Aqsa Martyrs' Brigade, an offshoot of Fatah.
Last week, the Palestine Liberation Organisation's parliament called for the disbanding of both groups.
The news came as an Israeli official pledged "dramatic" action to improve conditions for Palestinians in the West Bank.
Israeli Prime Minister Ehud Olmert's spokeswoman, Miri Eisin, said the country planned to "improve access and movement" for those living in the area, according to AP.