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.”

Israel imposed a naval blockade on Gaza in 2009, saying it was needed to prevent the smuggling of arms to the Islamic militant group Hamas, which governs the Palestinian enclave, and to jihadist groups operating there.

Mr. Heap said the Estelle was the latest of more than a dozen ships that had tried to break the blockade since 2010, when Israeli commandos killed nine pro-Palestinian activists after encountering resistance during a raid on a six-ship flotilla led by the Turkish vessel the Mavi Marmara.

After the Mavi Marmara raid, a United Nations panel found that Israel’s naval blockade was “legitimate self-defense and that Israel’s decision to intercept the flotilla was indeed legal under international law.” Activists have disputed the panel’s conclusion.

The episode led some of the restrictions on imports to Gaza to be relaxed, but also caused a deep rift in relations between Israel and Turkey, which has indicted four Israelis for their roles.

Among other things, the Estelle was carrying an anchor for a project called Gaza’s Ark, in which activists are building a boat intended to break the export curbs. “We carry humanitarian supplies,” Jim Manly, the former Canadian lawmaker who was on board, said in a statement posted online last week. “Our only ‘dangerous cargo’ is a cargo of hope.”

A spokesman for the Israel Defense Forces, Eytan Buchman, said the Estelle was the third such ship the military had boarded in two years. The military said that the boarding “was carried out in accordance with international law” and after repeated unsuccessful attempts to deter the ship through diplomatic channels and contact with passengers.

On Saturday, Prime Minister Benjamin Netanyahu of Israel issued a statement praising the operation and condemning the attempt to break the blockade.

“The people who were on the ship also know that there is no humanitarian crisis in Gaza, and they aim only to provoke and blacken Israel’s name,” the statement said. “If human rights were truly important to these activists, they would sail to Syria. We shall continue to defend our borders.”