The latest strike, which also wounded four people, took place in the town of Jabaliya, the target of at least three air strikes on Friday night.
A rescue worker was killed and a colleague wounded in a second missile strike at the scene, the sources said.
In a dozen such air raids which Israel said targeted militants preparing attacks, three other people, including two armed militants, were killed earlier on Friday in Beit Hanun and Beit Lahya in northern Gaza and in Rafah in the south.

Copyright AFP (Agence France-Presse), 2006