Palestinian terror groups will continue to try to kidnap IDF soldiers in the coming weeks, senior defense officials warned on Wednesday, after four terrorists infiltrated from Gaza and killed two Israelis. Dor Alon employees Oleg Lipson, 37, and Lev Cherniak, 53, both from Beersheba, were killed at the Nahal Oz fuel depot, which supplies fuel to Gaza. The afternoon attack took place hours after a soldier from the Golani Brigade's elite Egoz reconnaissance unit - St.-Sgt. Sayef Bisan, 21, from Jatt in the Galilee - was killed in clashes with terrorists in the central Gaza Strip. Defense Minister Ehud Barak threatened to retaliate against Hamas for the Nahal Oz attack. Defense officials said it was likely that the Nahal Oz crossing - used to transfer fuel and cooking gas to the Gaza Strip on a daily basis - would remain closed for a number of days. "Hamas is responsible for the attack and will bear the consequences when the time comes," Barak said in a phone conversation with visiting Polish Prime Minister Donald Tusk. "Hamas is in charge of the Gaza Strip and is responsible for every terror attack that originates there, including the one against the crossing." Four terrorists drove a car up to the border fence near the Nahal Oz fuel depot, undercover of a mortar barrage, the IDF said. The Gazans jumped out of the car, cut a hole in the fence and infiltrated the Israeli side of the crossing. By the evening, the IDF and Shin Bet (Israel Security Agency) had killed members of the terror cell who escaped from the crossing following the attack. Islamic Jihad, the Popular Resistance Committees and the Mujahedeen Brigades claimed responsibility for the attack. IDF sources said a probe would be opened to determine how the terrorists had succeeded in driving to the border fence without being spotted. Despite the failure, the IDF's quick response, OC Southern Command Maj.-Gen. Yoav Galant said, prevented additional casualties and thwarted the terrorists' ultimate goal - the kidnapping of a soldier. Defense officials said the terrorists' objective was probably to abduct Israelis, bring them to Gaza and use them as bargaining chips alongside Cpl. Gilad Schalit, who was kidnapped by Hamas in June 2006. "The terrorists most probably wanted to perpetrate a more serious attack such as a kidnapping or infiltration of a nearby [Israeli] community," Galant said. The two Israelis killed in the attack were employed at the terminal, which supplies Gaza with the fuel needed to power the Strip's sole power plant. Two of the terrorists were killed by the IDF at the terminal, and at least two others fled back to Gaza. In a swift response, the military dispatched aircraft, which bombed a car, killing two additional terrorists who were involved in the attack. Palestinians said that at least four more people, including children, were killed by the bombings. Earlier in the day, Bisan was killed when his unit was caught in a well-laid Palestinian ambush during counterterror operations in the central Gaza Strip. The soldiers from the Golani Brigade unit were searching for terrorist infrastructure near the Kissufim crossing, which was the main crossing to Gush Katif before Israel's unilateral withdrawal from Gaza in 2005. As the soldiers searched the area, they came under small-arms and anti-tank rocket fire. Bisan was killed and two of his comrades were lightly wounded. The troops returned fire and according to Palestinian reports one Hamas gunman was killed and at least four were wounded. Prime Minister Ehud Olmert said Hamas bore responsibility for the Nahal Oz attack and would pay a price, but his associates hinted that the prime minister would not support cutting off fuel supplies to Gaza. His associates said Olmert had told Palestinian Authority President Mahmoud Abbas on Monday that Israel would not create a humanitarian crisis in Gaza. They said Olmert did not want to play into the hands of Hamas, which had an interest in creating such a crisis in the Strip. "The fact that the terrorists in Gaza targeted the main fuel supply for Gaza in an attempt to kill people and destroy the fuel terminal demonstrates clearly their disregard for the well-being of the civilian population of Gaza," Olmert's spokesman Mark Regev said. "The truth is that Hamas is holding the civilians in Gaza and southern Israel hostage to its extremist, jihadic agenda." The Foreign Ministry released a statement reiterating that Hamas would bear the consequences for the attack. "This terror attack proves once more that not only do the terrorists in the Gaza Strip target Israelis, but they also try to harm the civilian infrastructure that enables normal life in Gaza," the statement read. "Anyone can see that the objective of the terrorists is to kill as many Israelis as possible and to undermine any expression of coexistence between Israel and Palestinians. "Israel transfers food, fuel, medicine, supplies and humanitarian aid to the residents of the Strip on a daily basis, and the terrorists who attacked the Nahal Oz crossing today are trying to sabotage this activity. In doing so, they are mainly damaging their own lives and the well-being of the residents of the Strip. Israel will know how to defend itself and will act against the terror organizations and their operatives while simultaneously maintaining its efforts to avert a humanitarian crisis in the Gaza Strip," the statement read. Environmental Protection Minister Gideon Ezra (Kadima) and ministers from Shas called on the government to stop supplying gas to the Gaza Strip. MK Avigdor Lieberman (Israel Beiteinu) said that "the murderous terror attack could have been prevented if the government would halt the supply of fuel and electricity to the Gaza Strip." "The government needs to disengage from Gaza, as I've said before," he concluded. Elie Leshem contributed to this report.