Rocket fire on the western Negev continued Wednesday, in response to an IDF operation in which troops thwarted an attempt by Palestinian gunmen to plant an explosive device along the Gaza border on Wednesday. Paratroopers on patrol identified a group of gunmen some 300 meters inside Gaza, near the Kissufim border crossing, and opened fire in their direction, the IDF said. Four Palestinian gunmen were killed in the ensuing exchange of fire. The soldiers crossed the border and entered the Strip in pursuit of the gunmen, and the terrorists set off explosives during the incident. One IDF soldier suffered light wounds to his hand and was evacuated to Soroka Hospital in Beersheba for treatment. A subsequent search of the terrorists' bodies revealed AK-47s and grenades. Shortly after the firefight, Palestinians fired a number of mortar shells, which landed on the Israeli side of the Kissufim crossing, and the IAF carried out two air strikes in the Khan Yunis area. Hours later, Islamic Jihad fired six mortar shells at Israel, which landed in open territories. No casualties were reported. Two Kassam rockets landed in the western Negev last night. No one was hurt and there was no damage. The army said there had been a significant rise in terrorist attempts to plant explosives along the border in recent days, as part of an effort to attack army border patrols. Defense Minister Ehud Barak addressed the incident during a visit to Military Intelligence headquarters in Tel Aviv. "This morning, very near the spot where last week a ticking tunnel was uncovered, a clash took place involving the same young paratroopers we met on our tour [of the Gaza border] yesterday," he said, praising their quick response. Hamas threatened to attack following the incident. "The anger of our people and our resistance will reach everybody, God willing, and our response to the enemy will be painful and will spill the Zionists' blood," spokesman Abu Obeida said in a statement. Hamas stopped short of saying the truce was over, but said gunmen would fight any entry of IDF troops into Gaza. "This is a clear violation of the truce, and the resistance has every right to respond to an attack," said Hamas spokesman Fawzi Barhoum. The latest clash came one day after Prime Minister Ehud Olmert visited the IDF's Southern Command, where he was briefed on the preparations being made by a Hamas-led coalition of terror groups. Israel and Hamas were on an inevitable collision course, Olmert said following the briefing. "It is merely a question of when and not a question of if," he warned. Barak, who accompanied Olmert on the visit, added, "The IDF is prepared, alert, and ready for any possibility. We are looking at this relative calm around and we know that many things are happening beneath the surface." Israel will allow a limited amount of fuel and humanitarian supplies into the Gaza Strip on Thursday. Defense Minister Ehud Barak took the decision after consultations with security officials. Last week, IDF special forces raided a tunnel dug by Hamas near the border, which the army said was to be used in an imminent kidnapping attempt. The raid left a number of Hamas gunmen dead and led to over 60 rockets being fired on the South in the following days, as well as a number of IAF air strikes on rocket-launching crews. AP contributed to this report.