Palestinians hit an Israel Air Force helicopter flying over the Gaza Strip with machine gun fire Friday but the aircraft returned safely to Israel with no casualties, Israeli security officials said.

Hamas said its men fired at the chopper as it raided a rocket-launching site in the northern Gaza Strip and reported hitting the aircraft.

"This afternoon our anti-aircraft crew opened fire at an Israeli aircraft over north Gaza, we know that it was hit," said Abu Obeida, spokesman for Hamas military wing.

Abu Obeida said Hamas would continue to try to target IAF aircraft with ever-improving munitions at their disposal. "This is a message from the Qassam Brigades that we are doing our utmost to confront Zionist planes ... and we will continue to try to hit them with more accurate weapons," he told Reuters.

The Israel Defense Forces would not comment officially, but security officials said the aircraft suffered light damage and landed safely in Israel with its crew unharmed.

Meanwhile Friday, Palestinian militants in the Gaza Strip fired three Qassam rockets at Israel during a visit by Deputy Defense Minister Matan Vilnai to the western Negev town of Sderot.

The rockets struck in open fields outside Sderot and no injuries or damage were reported.

Senior officials within the IDF told Haaretz Thursday night that the week-long lull in the fighting between Israel and Palestinian militants in Gaza seemed to have come to an end.

On Thursday, rockets and mortars rained on Sderot and other communities bordering the Gaza Strip as Palestinian militants responded to the killing Wednesday of four Islamic Jihad gunmen in Bethlehem.

The attacks Thursday broke a week of relative calm in the fighting. Thus far, the IDF has refrained from any response to the rocket and mortar attacks.

None of the latest attacks have caused serious damage or casualties. Most rockets and mortars fell on open fields.

The IDF attacked a rocket launcher in the Strip on Thursday, after carrying out no operations in the area for several days. Thursday's rocket attacks were the work of Islamic Jihad. Aside from the killing of its four men Tuesday, the same day the IDF killed another militant in the West Bank.

The role of Hamas in Thursday's attacks is not clear.

Defense Minister Ehud Barak said Thursday that Israel proved in Bethlehem and the killing of the four lslamic Jihad militants that it will continue to "hunt and target every killer who has Jewish blood on his hands."

Senior IDF sources said that even though Hamas does not appear to be responsible for Thursday's rocket attacks, it is not making any effort to restrain Islamic Jihad and prevent the bombardment. They added that it is doubtful whether Hamas will choose in future to confront the various militant factions to prevent an escalation with Israel.

IDF sources said it is most likely that in the near future there will be another direct confrontation between Israel and the militant factions in the Strip.

The Prime Minister's Office said Thursday that Israel holds Hamas accountable for every rocket fired by the different militant groups in the Gaza Strip.

"When another group publicly takes responsibility, as happened earlier today, such a group could not be shooting rockets without the acquiescence and collaboration of Hamas. We will not allow Hamas to sub-contract out terrorism," said Mark Regev, a spokesman for Prime Minister Ehud Olmert.

Islamic Jihad claimed responsibility for some of Thursday's rockets, saying the attacks were in response to Tuesday's raid in Bethlehem.

Former Deputy Defense Minister Ephraim Sneh said Thursday that Hamas had to be toppled before rocket fire would stop.

"Israel will not exist side by side with this Iranian entity three kilometers from Sderot and 10 kilometers from Ashkelon," Sneh told Army Radio. "There can be no solution without a diplomatic agreement, and there can be no solution without the military wiping out Hamas."

According to the assessments of the defense establishment, Hamas is interested in a long-term cease-fire but is setting conditions for an agreement that are unacceptable. Hamas has insisted that the IDF and the Shin Bet need to cease all operations and arrests in the West Bank for a cease-fire agreement.

Defense officials expect the lull in the fighting to end and be followed by further fierce fighting. Only after Hamas suffers severe blows do the defense officials believe the radical Islamic group will agree to soften some of its demands.

According to Palestinian sources, the commitments made by Hamas to the Egyptian negotiators was only for a week of quiet, scheduled to end Friday.

The Palestinian Authority published a statement denouncing the Israeli operations in the West Bank.