Israeli authorities on Saturday began deporting pro-Palestinian activists who tried to breach the naval blockade of the Gaza Strip.

The Israeli navy on Friday intercepted a Canadian vessel and an Irish boat carrying 27 activists and medical supplies which had set sail from Turkey toward Gaza.

An Israeli Immigration Authority spokeswoman said two Greek citizens were flown home on Saturday and two journalists, one American, and one Spanish, were to board flights on Sunday.

One Israeli citizen was released, as was an Egyptian woman who had crossed back to neighboring Egypt overnight, the spokeswoman said. Twenty one other activists were being held in custody in Israel and were awaiting deportation.

Israel's navy has intercepted similar protest ships in the past, towing them to 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.