Hantman said militants have tried in the past to smuggle weapons into Gaza by sea. In 2011, a vessel carrying 50 tons of weaponry sought to reach Gaza, while in 2009, a boat tried to bring in some 500 tons of weapons, he said.
A Hamas spokesman condemned Israel's actions as "piracy."
"This confirms that the (Israeli) occupation is maintaining its control and isolation of Gaza. There must be more flotillas of solidarity activists to Gaza," said Fawzi Barhoum.
Associated Press writers Ibrahim Barzak in Gaza City and Karl Ritter in Stockholm contributed to this report.
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