The IDF has stepped up its efforts against the terror infrastructure in Gaza and, in a 36-hour operation that ended Thursday, discovered seven weapons-smuggling tunnels in the southern Strip along the Egyptian border. The kilometer-long tunnels were discovered near Dahiniye by an elite Engineering Corps unit and troops from the Golani infantry's Battalion 51. The tunnels were found within two kilometers of the border with Israel and, according to the IDF, had been used intensively in recent months to smuggle weapons and explosives from Egypt into Gaza. The troops destroyed the tunnels in controlled explosions. IDF sources said they had been large enough for people to pass through and were most probably used by terrorists to leave Gaza on their way to Iran or Syria for training. The army estimates that terrorists have dug dozens of tunnels over the past year. Shin Bet (Israel Security Agency) chief Yuval Diskin told the Knesset Foreign Affairs and Defense Committee Monday terrorists had smuggled more than 112 tons of explosives into Gaza since Israel's disengagement from the Strip in 2005. Noting the difficulty in obtaining intelligence on the tunnels' locations, defense officials said Israel expected Egypt to step up its efforts to thwart the weapons smuggling by clamping down on the tunnel industry in Sinai. "The Egyptians can do more with the military force they have along the border," a defense official said. "We hope that this discovery [of the tunnels] will motivate them to act." Earlier Thursday, nine Kassam rockets were launched into the western Negev, including four that struck Sderot. In response, the IDF bombed two Kassam launchers in northern Gaza. The Home Front Command placed eight concrete bunkers around the town Thursday morning. It was not clear if the move was directly connected to the rocket attacks. Another 43 will be placed in Sderot by the end of the month, the Defense Ministry said. Also Thursday, the IDF shot and killed five terrorists who were spotted planting bombs along the Gaza security fence. In response, the Fatah Al-Aksa Martyrs Brigades threatened to fire hundreds of rockets at Israel. The group announced the commencement of "Operation Gaza Autumn," to include an escalation in rocket fire. In a flyer distributed Thursday morning it said it had "not tired of the resistance." "Autumn 2007 is arriving without a national unity government. We hear talk of summits here and there. We are marking 90 years since the evil Balfour Declaration, continuing IDF operations into Gaza, killings of Palestinians and destruction of houses," the flyer read. In the West Bank, an elite IDF unit nabbed the top Hamas commander in Nablus's Balata refugee camp, thought responsible for dozens of attacks against soldiers and civilians. Omar Isa was caught in a home together with an M-16 rifle and a pistol. And a 16-year-old Palestinian boy was caught at the Hawara checkpoint south of Nablus with four bombs hidden on his body. The devices were destroyed by Border Police sappers.