Israeli troops shot the three heavily armed men when they crossed the Egyptian border and ambushed the soldiers, averting "a very big terror attack”, an Israeli military spokeswoman said on Friday.The incident took place on the Israeli side of the frontier at a place called Har Harif, which is almost half way down Israel’s 240km border with the Egyptian Sinai Peninsula."Three armed terrorist entered from the Sinai into Israel,” army spokeswoman Lieutenant Colonel Avital Leibovich told reporters."They opened fire toward IDF (army) troops that were guarding the workers (building the fence) in that area. Another force that was nearby... rushed to the area and targeted those three terrorists,” she said."All three terrorists were killed.”She said the men were "very well armed and prepared” in terms of equipment, and were also wearing explosives belts."A very big terror attack was thwarted by the quick response of these soldiers,” Leibovich said, ruling out the possibility that any further armed men had infiltrated Israeli territory.Border security incidents have increased over the past 18 months as a wave of lawlessness has gripped the Sinai since the overthrow of veteran Egyptian president Hosni Mubarak.On June 18, at least three armed men cross the border from Sinai and ambushed two cars carrying Israeli construction workers, killing one and sparking a firefight with the army in which two of the attackers died. The third fled back to Egypt.