EILAT, Israel -- Gunmen who crossed from the Egyptian desert launched a series of attacks in southern Israel Thursday, killing eight people and threatening to destabilize a volatile border region that includes the Hamas-ruled Gaza Strip and the increasingly lawless Sinai Peninsula.
Israel blamed an armed Palestinian group from neighboring Gaza.
Israeli forces killed five of the gunmen along the border with Egypt, the military said, and later launched an airstrike inside Gaza that killed five other militants from the same group as well as a child.
Gunfire continued on both sides of the border late into the evening.
After nightfall, Israel's "Iron Dome" anti-missile system intercepted a rocket fired by Gaza militants at the city of Ashkelon, the military said.
The attacks were the deadliest against Israelis since a gunman killed eight civilians in Jerusalem in 2008.
The attacks suggested that Egypt's recent political upheaval and a resulting power vacuum in Sinai had allowed militants to open a new front against Israel on the long-quiet frontier.
The attack began shortly after noon in southern Israel with gunfire at a civilian bus heading toward the Red Sea resort city of Eilat.
A number of passengers were hit, the military said. The gunmen had crossed the border and set up an ambush armed with automatic weapons, grenades, and suicide bomb belts, according to the military.
Within an hour, gunmen had riddled another passing bus and two cars with bullets and rigged a roadside bomb that detonated under an army vehicle rushing to the scene.
At the same time, mortar gunners in Gaza opened fire at soldiers along the Gaza-Israel border fence.
The Israeli dead included six civilians and one soldier, according to the Israeli military's southern commander, Maj. Gen. Tal Russo. A member of an elite police counter-terrorism unit also was killed, accounting for the eighth Israeli fatality, according to Chief Inspector Alex Kagalsky, a spokesman for the Israel police.
Israeli soldiers eventually killed five attackers, the military said, and defense officials said three of the bodies were wired with explosives.
"Today we all witnessed an attempt to step up terror by attacking from Sinai. If anyone thinks Israel will live with that, he is mistaken," Prime Minister Benjamin Netanyahu said last night.
"If the terror organizations think they can strike at our civilians without a response, they will find that Israel will exact a price -- a very heavy price."