KIBBUTZ KEREM SHALOM, Israel – Israel was poised for a retaliatory strike last night after two of its soldiers were killed and another kidnapped in a dawn attack by Palestinian Arab terrorists who tunneled under Gaza’s heavily protected border.

With the fate of the kidnapped soldier unclear, Israel’s defense minister, Amir Peretz, issued a clear threat of revenge if the hostage was hurt or killed.

He was named as Corporal Gilad Shalit, 19, and Israeli trackers said they found his blood-stained bulletproof vest close to the Gaza perimeter fence. Terrorists loyal to Hamas, the Palestinian ruling party, claimed “partial” responsibility for the attack.

The Hamas political leadership sought to distance itself from the incident last night when a spokesman said it had no knowledge of the fate of Corporal Shilat. The spokesman, Ghazi Hamad, said: “We are calling on the resistance groups, if they do have the missing soldier … to protect his life and treat him well.”

Israel, however, blamed Hamas for the incident, which has plunged relations to a new low since last September’s withdrawal of Jewish settlers and Israeli soldiers from the Palestinian Arab territory.

The attackers, believed to number seven or eight, surprised Israeli forces when they appeared at first light through a tunnel on open ground 300 yards inside Israel near a kibbutz.

They split into three groups before launching simultaneous attacks on three Israeli defensive positions, a lookout tower, a tank, and an armored personnel carrier, both dug-in, facing Gaza. They blew open the tank’s rear doors with a missile fired from point-blank range before tossing grenades inside.

Two of the tank crew died and another was severely wounded, but the final crew member, the gunner, was forced out of the wreckage at gunpoint.

Meanwhile, two other terrorists attacked a nearby concrete watchtower. One got inside and was climbing the spiral stairs when Israeli soldiers in the guardroom at the top of the tower fired down the stairwell and killed him, according to defense sources.

A second terrorist was shot dead as he fled from the watchtower across open sandy ground. The troop carrier was also damaged in another attack but it was unoccupied.

The attackers then escaped back into Gaza by cutting their way through the perimeter fence. Later, three Israeli tanks followed them into Gaza, supported by an Israeli attack helicopter, but they could find no trace of the fugitives.

While more than 25 Palestinian Arabs, mostly civilians, have died in recent violence, the two soldiers were the first Israeli deaths, prompting calls within the Jewish state for a massive military response. Army commanders were drawing up plans for offensive ground operations, but their hand was stayed by uncertainty surrounding the kidnapped soldier.

The last similar incident was in 1994 when Corporal Nachson Waxman, a 19-year-old Israeli-American, was abducted. Israeli commandos stormed the safe house where Waxman was held, but he died in the raid.

Last night Shin Beth, the Israeli spy agency, was tapping into its extensive collaborator network in Gaza to try to locate Corporal Shalit.

With Hamas’s armed wing, the Izzedine Al-Qassam Brigades, saying it supported the operation, primary responsibility was taken by the Popular Resistance Committees, a small but increasingly active terrorist brigade.