JERUSALEM — The Israeli Navy on Saturday seized a European ship headed to the Gaza Strip to try to break Israel’s maritime blockade against the Hamas-controlled region and diverted it to an Israeli port.

The military said that the ship, the Estelle, had been seized without incident and taken to the port of Ashdod, in southern Israel, and that the more than two dozen people on board, including five European lawmakers and a former Canadian legislator, would be turned over to the police.

Advocates supporting the mission said the vessel had been surrounded by warships, and they called the boarding an “assault.”

“The last contact we have from our people on board was that they were going to be boarded,” said David Heap, an activist who was attending a conference in Gaza. “We have no confirmation from them of how they are, and we may not for some time hear directly from them.”