"The vessels broke free from their moorings and two vessels are now anchored on the beach near the pier. The third and fourth vessels are beached on the coast of Israel near Ashkelon," the statement said.

"No US personnel will enter Gaza. No injuries have been reported and the pier remains fully functional," it continued, adding that the Israel navy is assisting with recovering the vessels.

Gaza is suffering through its bloodiest ever war, which broke out after Hamas's unprecedented attack on October 7 resulted in the deaths of more than 1,170 people, mostly civilians, according to an AFP tally of Israeli official figures.

Israel's retaliatory offensive has killed at least 35,800 people in Gaza, mostly women and children, according to the Hamas-run territory's health ministry.

Israel has imposed a siege on Gaza that has deprived the territory's 2.4 million people of most clean water, food, medicines and fuel.

US President Joe Biden had said in March the pier would be built to alleviate restrictions imposed by Israel on delivery by land to Gaza.

The UN World Food Programme "took possession of 97 trucks since the floating dock came into operation" on May 17, Stephane Dujarric, spokesman for UN chief Antonio Guterres, told reporters on Friday.

In the first few days of deliveries, desperate people made off with the contents of some trucks heading to warehouses, but the situation has now stabilized, he said.