Israel troops board Gaza protest boat Dignite-al Karama
Israeli commandos have intercepted and boarded a boat trying to breach Israel's blockade of the Gaza Strip.
The Dignite-al Karama, the sole representative of an initial 10-vessel flotilla, had earlier been warned to change course.
The Israeli military said the boat had been boarded peacefully. It was later escorted into the Israeli port of Ashdod.
An anti-blockade protest group said the boat had been in international waters.
Maxime Guimberteau from A French Boat for Gaza said activists on board the Dignite-al Karama had told him they were 40 nautical miles off the coast of Gaza when the boat was surrounded by four Israeli navy ships. He said their conversation then cut off.
Responding to the news that Israeli commandos had boarded the boat, another French-based group, Platform Palestine, told the Associated Press news agency that Israel's action clearly showed "the military logic of Israeli politics, which only speaks the language of force".
Platform Palestine said it had not been in contact with anyone on board the Dignite-al Karama.
The Hamas government in Gaza also condemned the takeover of the vessel.
An Israeli Defence Force statement said the Dignite-al Karama had been boarded "after all diplomatic channels had been exhausted and continuous calls to the vessel had been ignored".
It said the navy had started a dialogue with the activists five hours earlier.
"Upon expressing their unwillingness to arrive at the Ashdod port, it was unequivocally necessary to board the vessel and lead it there," the statement said.
"The soldiers operated in line with procedures and took every precaution necessary... [to] avoid causing harm to the activists on board while ensuring the safety of the soldiers."
Hours later, the ship entered the port city of Ashdod flanked by three small Israeli naval vessels, witnesses said.
Israeli officials said those on board would be turned over to the Israel police, the immigration authority and the interior ministry at Ashdod.
The Dignite-al Karama is part of Freedom Flotilla II, which has been trying to deliver humanitarian aid to Gaza since the end of June. Flotilla organisers say despite the opening of Gaza's Egyptian border, the territory remains under "unlawful blockade" by the Israelis.
In an earlier statement, the Israeli military said the aid could be delivered through existing land crossings without breaching the blockade.
In 2010, nine Turkish activists were killed when Israeli commandos boarded the lead ship of the first Freedom Flotilla, causing an international outcry.
As a result, Israel eased its blockade on Gaza, which it says is necessary to stop weapons smuggling and put pressure on Hamas.
However, relations between Israel and Turkey were damaged by the incident.
Turkish Prime Minister Recep Tayyip Erdogan said on Tuesday he was considering visiting the Gaza Strip "if conditions allow".
He told reporters he would like to cross to Gaza during a visit to Egypt currently being planned.
Israel increased sanctions on the impoverished Palestinian territory in 2006 after militants captured Israeli soldier Gilad Shalit. Israel tightened them further still a year later when Hamas ousted rival Palestinian organisation Fatah from the territory.
Although the Islamist group won Palestinian legislative elections in January 2006, it refuses to recognise Israel or to renounce violence and is designated in the West as a terror organisation.