Maj. Eliraz Peretz and Staff Sgt. Ilan Sviatkovsky were killed in the Gaza Strip Friday while pursuing a group of Palestinian militants trying to lay mines near the order fence. Two other soldiers were injured in the incident, and two militants were killed.

Unusually, Hamas claimed responsibility for the clash, even though it is likely that the militants belonged to the Islamic Jihad group.

GOC Southern Command officers said yesterday that the IDF force commanded by the deputy commander of Battalion 12 of the Golani Brigade, Eliraz Peretz, operated in line with regulations and entered the Gaza strip in order to prevent Palestinian militants from laying mines near the fence.

Peretz, 32, from Eli in the West Bank, lost his elder brother, Lieutenant Uriel Peretz, 12 years ago in southern Lebanon. Sviatkovsky, 21, was from Rishon Letzion.

A force of some 20 Golani infantrymen under the command of Major Peretz gave chase to a group of Palestinians seen laying mines near the fence, about midday Friday. Several hundred meters inside the Gaza Strip, the militants opened fire against the soldiers. An initial investigation of the incident showed that a bullet struck a hand grenade in Peretz's ammunition belt, causing it to explode. Peretz was killed by the explosion, while Sviatkovsky was hit by gunfire.

Another soldier, Guy Elmakayes, who was the force's radioman, was seriously injured by gunfire. A Bedouin tracker with the force suffered light injuries. The remaining force engaged the Palestinians at a distance of about 15 meters.

GOC Southern Command, Maj. Gen. Yoav Gallant, said that initial findings suggest that the soldiers reacted professionally, as they are expected to.

In a separate incident several hours later, an armored force attacked another group of militants trying to lay mines, hitting two. Palestinian sources reported that in both cases Israeli tanks and armored bulldozers entered the Gaza Strip and destroyed a number of structures.

What is new in Friday's incident is that Hamas claimed responsibility. Senior IDF and Shin Bet security service sources have maintained that since Operation Cast Lead, Hamas has avoided carrying out direct attacks against the IDF or inside Israeli territory. In most cases, Hamas authorities in the Gaza Strip have gone out of their way to restrain smaller Islamist factions responsible for the continued rocket attacks on Israel.

However, in recent weeks there has been a rise in the number of rockets fired. Three Qassam rockets were fired into Israel over the weekend, causing no damage or injuries.

Intelligence sources in Israel have recently raised the question whether Hamas was turning a blind eye to the rocket attacks, a possible change of tactics. Defense Minister Ehud Barak said on Channel 2 yesterday that Hamas is trying to change the "rules of the game" in the Gaza Strip, and will have to pay the price for this.

Spokesmen on behalf of Hamas claimed Friday evening that their gunmen acted defensively after an IDF force entered their area. In this they hinted that there was no change in policy from the point of view of Hamas. Responsibility for the incident was also claimed by three smaller factions in the Gaza Strip, including Islamic Jihad.

It is possible that Hamas was involved in the incident, in the mortar fire that was used to support the Palestinian gunmen during the exchanges of fire.

There is concern in the IDF that Hamas is trying to alter the situation along the fence, which will result in their targeting of Israeli patrols. Any change along the fence may present the Netanyahu government with the first military challenge of its tenure. For the past year the situation has been calm, in great part as a result of the two wars conducted by the Olmert government: the Second Lebanon War and Operation Cast Lead.

The incident comes at a convenient time for Hamas, on the eve of the Arab League summit, but for Netanyahu the timing is terrible, with pressure from the Americans and the international community on the need to alleviate the siege on the Strip.