Haaretz reports: Two protest boats approached the Gaza coast on Friday with the intent to violate Israel’s naval blockade of the territory and were met by Israeli navy vessels, Palestinian activists said.

In Gaza, activist Amjad Shawwa said the boats were about 50 miles (80 kilometers) from Gaza and had been warned over the radio by an Israeli navy ship to change course.

The Israelis told the boats, carrying supplies and 27 international pro-Palestinian activists, that they were entering a closed military zone, Shawwa said.

He said the passengers intended to continue to Gaza.

Activists in Gaza and Ramallah said they lost radio contact with the ships shortly after 1 p.m.

The Israel Defense Forces said that the Israel Navy had contacted the Gaza-bound ships and informed them that Gaza is under a maritime security blockade. The IDF told the ships they could turn around or dock in the Egypt or at the Ashdod port. The ships deed not heed that call and continued towards Gaza.

Israel’s navy has intercepted similar protest ships in the past, towing them to the Israeli port of Ashdod and detaining participants. Israel says its naval blockade of Gaza is necessary to prevent weapons from reaching militant groups like Hamas, the Iran-backed group that rules the territory. Critics call the blockade collective punishment of Gaza’s residents.

Israel’s government has said the activists can send supplies into Gaza overland.

In May 2010, nine Turkish pro-Palestinian activists were killed when they resisted an Israeli operation to halt a similar flotilla. Each side blamed the other for the violence.

The incident sparked an international outcry and forced Israel to ease its land blockade on Gaza, which was imposed in 2006 and tightened, with Egyptian cooperation, after Hamas seized control of the territory the following year.

Militants in Gaza have fired thousands of rockets into Israel in the past decade, and now have much of southern Israel in range.

Speaking after prayers at a Gaza City mosque, Ismail Haniyeh, the Hamas prime minister, addressed the passengers aboard the boats, saying, “Your message has been delivered whether you make it or not.”

“The siege is unjust and must end,” Haniyeh said.

On Thursday, the Obama administration warned U.S.citizens on the boats that they may face legal action for violating Israeli and American law. The activists include Americans and citizens of eight other countries.

State Department spokeswoman Victoria Nuland said the U.S.was renewing its warning to Americans “not to involve themselves in this activity.”

The U.S., like Israel and the European Union, considers Hamas a terrorist organization.