Palestinian militants said Tuesday they had launched a large number of floating explosives into the Mediterranean Sea to avenge the death of a top Hamas commander, a day after two bomb-laden barrels washed up on Israel's coastline.

Israeli authorities launched an intensive search for new bombs, closing miles of beaches, deploying robotic bomb squads and ordering surfers out of the wintry waters.

Israeli Prime Minister Benjamin Netanyahu blamed Hamas and hinted at retaliation.

Abu Saed, a spokesman for the Popular Resistance Committees, a Gaza faction with close ties to Hamas, said the attack was meant to avenge the killing last month of Mahmoud al-Mabhouh, a veteran Hamas operative who Israeli defense officials say was involved in smuggling rockets into Gaza [Some are saying he was assassinated by Arabs, not Israelis. -MS]...

..."We confirm that there are still many of these charges in the ocean, and they haven't exploded yet," Abu Saed said, standing alongside five other gunmen in military fatigues.

In Jerusalem, Netanyahu accused Hamas, which rules Gaza, of being behind the operation, with support from Iran and Syria.

"We view with great severity the Hamas operation near the Gaza beach, and we will respond accordingly," he said, without elaborating.

On Monday afternoon, a barrel bomb washed up on the beach of Ashkelon, about nine miles (15 kilometers) north of Gaza. A few hours later, another one was found at Ashdod, six miles (10 kilometers) farther north.

Each had about 22 pounds (10 kilograms ) of explosives, police said. They said bombs of that size could cripple small civilian vessels but not Israeli warships...