Israel carried out airstrikes in the southern Gaza Strip late Thursday after blaming Gaza militants for a series of deadly attacks in southern Israel.

Israeli Prime Minister Benjamin Netanyahu, in a televised address, warned that anyone who attacks Israel will pay a “very heavy price.”

The Israeli airstrikes are reported to have killed six people, including a leader of the Popular Resistance Committee, an armed Palestinian faction.

Earlier Thursday, gunmen in southern Israel killed at least seven people and wounded about 40 during a series of apparently coordinated attacks.

Israeli officials say the attacks took place in quick succession near the border with Egypt's Sinai Peninsula, north of the Israeli town of Eilat.

They say gunmen fired on a passenger bus and a private vehicle, targeted a military patrol and detonated explosives near security forces. Israeli media reports say Israeli troops tracked and killed seven suspected attackers.

Defense Secretary Ehud Barak called the attacks a grave terrorist incident. Barak and other Israeli officials asserted that the attackers came from the Hamas-ruled Gaza Strip and entered Israel from the Sinai. Hamas has denied involvement.

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.