Gunmen have killed at least seven people in a series of apparently coordinated attacks in southern Israel.

Israeli officials say the attacks took place in quick succession Thursday near the border with Egypt's Sinai Peninsula. They say at least 25 people were wounded.

Authorities say gunmen opened fire 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 and said his forces would react with strength and determination.

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.

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.