Five people, including a senior Palestinian security official, have been killed in a drive-by shooting in Gaza City.
Gunmen opened fire on a car carrying Jad Tayeh, a senior figure in the Palestinian intelligence services, killing him and four others.
Supporters of rival Hamas and Fatah factions have often clashed in Gaza since Hamas won elections in January.
Hamas this week agreed to join Fatah in a national unity government.
The deal, between the Hamas Prime Minister Ismail Haniya and the Fatah Palestinian Authority (PA) President Mahmoud Abbas, raised hopes that a block on international aid to the PA could be lifted.
Correspondents say the deal was also aimed at easing internal tensions between the rival factions.
Friday's attack happened near the Beach refugee camp in Gaza City, close to Mr Haniya's office.
Unidentified attackers shot dozens of bullets into the car, residents and officials said.