Israeli military aircraft carried out a fourth day of airstrikes in the Gaza Strip on Tuesday, and Israel's defense chief suggested that leaders of the radical Palestinian group Hamas might be assassinated if rocket fire into southern Israel did not stop.

Defense Minister Shaul Mofaz singled out Hamas leaders Ismail Haniyya and Mahmoud Zahar in his warning. He said that unless attacks from Gaza ceased, Israel would send the men "to where Abdel Aziz Rantisi and Sheik Yassin are."

Ahmed Yassin, one of the founding leaders of the Islamic Resistance Movement, as Hamas is formally known, was killed last year by an Israeli missile strike in Gaza City. Israel assassinated Rantisi, who succeeded Yassin, less than a month later. Israeli officials have said they would respond to attacks from Gaza far more vigorously after ending Israel's 38-year presence in the strip earlier this month.

"As long as there is no quiet, the terror groups will know no quiet," Mofaz told reporters as he visited Israeli soldiers along Gaza's border

The warning came as Hamas and a dozen smaller armed factions, including Islamic Jihad, announced that they would abide by the terms of a temporary cease-fire with Israel that was reached in March. The truce has been shaken several times, most recently when Israeli forces killed three Islamic Jihad fighters last week near the West Bank city of Tulkarm and Palestinian groups fired a barrage of homemade rockets into Israel, wounding at least five civilians.

The Israeli military responded to the rocket attacks by killing at least two Hamas fighters and the military leader of Islamic Jihad for southern Gaza. In several pre-dawn strikes Tuesday, Israeli military aircraft hit an office building used by the ruling Fatah movement and a currency exchange shop used by Hamas to transfer money, military officials said. The military also struck roads in northern Gaza used by Palestinian fighters to reach rocket-launching areas.

During the day, several rockets fell in southern Israel, including one Tuesday evening that landed inside the city of Sderot. Less than an hour later, the Israeli military fired artillery into an open field in northern Gaza where military officials said the rocket had been launched. Early Wednesday, an Israeli attack helicopter fired missiles into an office building used by Fatah, witnesses said. No injuries were reported.

Also Tuesday, the armed wing of Hamas asserted responsibility for the killing of Sasson Nuriel, an Israeli businessman kidnapped Sept. 21. His body was found Monday near the West Bank city of Ramallah.

Hamas released a videotape Tuesday showing him kneeling and blindfolded before a green Hamas banner. In a statement, the group claimed that Nuriel was an agent for Shin Bet, Israel's domestic security service. The group said it had planned to trade Nuriel for the release of Hamas members in prison. The statement said he was killed because of pressure from Israeli military operations in the West Bank.

Special correspondent Islam Abdel Kareem in Gaza City contributed to this report.

A Palestinian woman looks on as Israeli soldiers seek Palestinian fighters in Dahariya in the West Bank.