Israeli military forces have intercepted Global Sumud boats using jamming technology and armed boarding teams to halt the humanitarian fleet in the middle of the Mediterranean, according to organisers and Israeli media.

“Our boats were approached by military speedboats, self-identified as ‘Israel’, pointing lasers and semi-automatic assault weapons, ordering participants to the front of the boats and to get on their hands and knees,” the Global Sumud Flotilla aid mission said on Thursday.

“Boat communications are being jammed, and a SOS was issued.”

Israel Army Radio cited an Israeli source as saying it began seizing control of aid ships heading towards Gaza, far from Israeli shores. It added that naval forces had captured seven of 58 vessels in the Global Sumud Flotilla near the Greek island of Crete.

A spokesperson for the Global Sumud Flotilla has described Israel’s boarding of its vessels as “a straight-up attack on unarmed civilian boats in international waters”.

Press officer Gur Tsabar, speaking to Al Jazeera from Toronto, Canada, said the sea assault was taking place “hundreds of miles from Israel”, with the flotilla being “surrounded and threatened at gunpoint”.

“This is illegal under international law. Israel has no jurisdiction in these waters. Boarding these boats amounts to illegal detention – potentially kidnapping on the high seas,” said Tsabar.

“It’s critical that all governments act now. Every government has an obligation to protect the over 400 civilians on board and to uphold international law. Silence in this moment is absolute complicity.”

Al Jazeera Arabic reported that the Israeli army has issued warnings to activists on board the flotilla’s ships, demanding they return immediately, and threatening to intercept the ships and obstruct their arrival “by all possible means” if they continue sailing.

Gaza has been devastated by more than two years of Israel’s genocidal war, which killed more than 72,500 Palestinians.