The Israeli Navy has boarded two protest vessels which were attempting to reach Gaza in violation of Israel's maritime blockade.
The two yachts, believed to be carrying 27 pro-Palestinian activists, ignored repeated calls to turn around or divert to the Israeli port of Ashdod, according to the country's military.
"The decision was made to board the vessels and lead them there," the military said in a statement.
No one was injured in the incident which Israel has described as an act of "provocation".
The activists on board the yachts will be handed over to the custody of the police and immigration officials in Israel.
Israel had been monitoring the progress of the Canadian and Irish vessels since they set sail from Turkey on Tuesday as part of a campaign called Freedom Waves For Gaza.
The New York-based organisers said they intended to reach Gaza to show solidarity with the 1.5million Palestinians there who they claim are being subjected to "collective punishment" by Israel's sea blockade.
They have indicated they will try to send more flotillas to Gaza in the coming months.
Israel says its blockade of the Gaza Strip is in place to prevent weapons being smuggled into the territory.
The United Nations has declared it to be legal under international law.
In 2010, nine Turkish activists were killed when Israeli commandos boarded another protest vessel, the Mavi Marmara, to prevent it reaching Gaza.
The incident has caused a diplomatic rift between Turkey and Israel.