Israeli planes hit rocket launch sites in Gaza early today, hours after a Palestinian suicide bomber killed at least three Israelis near a West Bank settlement.
Israel said yesterday's attack near the settlement of Kedumim followed dozens of warnings of impending attacks.
The Palestinian suicide attack was the first such bombing in two months. Rescue workers said the bomber was disguised as a religious Jew and was hitchhiking.
He talked his way into a car near the entrance to the settlement, then blew himself up. Hamas described it as a "natural response to Israeli crimes".
Israeli media said four Israelis had been killed in the attack.
Al-Aqsa Martyrs Brigades, part of the Palestinian President Mahmoud Abbas's Fatah movement, claimed the bombing and said it was in response to Israeli attacks.
Palestinian governments under Fatah's control had recently condemned suicide bombings inside Israel, though used more careful language when it came to attacks inside the West Bank, captured by Israel in the 1967 war.
The latest violence comes just days after militant Islamist group Hamas took office and Israeli leader Ehud Olmert's Kadima party won elections with a platform of imposing a border in the occupied West Bank if peacemaking remains frozen.
Final election results showed Kadima had won 29 seats in the 120-member parliament, up one from earlier counts. To form a government, Kadima will have to align with other parties.