Police on Wednesday said they had destroyed the third explosive device washed ashore in Israel this week.

Bomb disposal experts carried out a controlled explosion at Palmachim beach, some 10 kilometers south of Tel Aviv, police said.

Two barrels packed with explosive charges were picked up on Israeli beaches at Ashkelon and Ashdod on Monday. Two more are believed to have exploded on the shores of the Gaza Strip.

Each was of a similar size, containing between 15kg and 20kg of TNT explosives and designed to be detonated by a signal from a cellular telephone, a senior navy official told Haaretz on Tuesday night.

The barrels were probably launched from Palestinian fishing vessels, the official said, adding that it was likely more explosives would be found in the coming days.

On Monday the Gaza-based militant group Islamic Jihad reportedly claimed responsibility for dispatching the first two bombs.

During Tuesday night Israel launched air strikes against several buildings in Gaza and smuggling tunnels beneath Egypt's border with the strip, as a response to both the launch of the barrel bombs and to rockets fired at Israel from within the Hamas-controlled territory.

Late on Wednesday afternoon Army Radio reported that two more objects resembling the earlier barrel bombs had been spotted floating off Netanya.