Rocket propelled grenades were fired Tuesday at a security compound in the Gaza Strip, moderately wounding three maintenance workers, security and hospital officials said.
The agency is loyal to President Mahmoud Abbas and has been at the center of a power struggle between Abbas and his main rival, Hamas.
Officials in Abbas' Fatah movement blamed Hamas for the attack. Security personnel fired at the attackers, but the assailants escaped, officials said.
Hamas has accused the Preventive Security agency of being behind a wave of unrest in Gaza. Clashes between forces loyal to Abbas and Hamas have left 16 people dead in recent weeks.
Tuesday's attack came as Abbas was meeting in the West Bank with top officials ahead of an expected decree calling a referendum on a plan that implicitly recognizes Israel. Hamas opposes the referendum.
"This is a series escalation. Hamas is keen on exporting the battle over the referendum to the streets," said Fatah spokesman Maher Mekdad. Hamas officials were not immediately available for comment.