Israeli forces have killed at least 10 Palestinian militants in separate attacks after blaming them for a series of coordinated raids along the Israeli-Egyptian border that killed eight people and wounded 40 more.

Israeli troops shot five gunmen along the border, and Egyptian soldiers reportedly killed two more, but most of the attackers escaped. An Egyptian official said an Israeli helicopter gunship chasing militants near the border inadvertently killed an Egyptian army officer and two security personnel when they were caught in the line of fire.

Israel later launched an airstrike inside Gaza that killed five other militants, including a leader of the Popular Resistance Committee, an armed Palestinian faction.

The Israeli military said the raids occurred when gunmen crossed from the Hamas-ruled Gaza Strip into Egypt's Sinai Peninsula through a network of smuggling tunnels. They then allegedly traveled some 200 kilometers to reach an area along the Egyptian border near the southern Israeli city of Eilat.

Defense officials said gunmen fired on a passenger bus and a private vehicle, targeted a military patrol and detonated explosives near security forces. The assault began around midday Thursday. Hamas has denied involvement.

Israeli Prime Minister Benjamin Netanyahu, in a televised address, warned that anyone who attacks Israel will pay a “very heavy price.” Defense Secretary Ehud Barak called the attacks a grave terrorist incident.

The United States and the United Nations issued separate statements condemning the attacks in Israel. U.N. Secretary-General Ban Ki-moon also urged restraint.

Israel has expressed concern about a deterioration of security in the Sinai since Egypt's President Hosni Mubarak resigned in February.

Last week, Egypt moved additional forces to the region in an effort to improve security.