Organizers of a pro-Palestinian flotilla that will try to break Israel's sea blockade of the Gaza Strip accused Israel on Thursday of sabotaging a second ship.
There was no immediate word on how this would affect activists' plans to set off from the Greek port of Piraeus, the flotilla's base of operations.
Activist Huwaida Arraf told Israel's Army Radio that the engine of an Irish ship was damaged while in port. "When the engine was started, it completely bent," Arraf said. "While out at sea, if this would have happened, if it would have bent in this way, the boat would have started taking on water and it could have led to fatalities."
Earlier this week, activists said Israel damaged the propeller of a Swedish ship in Pireaus.
Israel has not commented on the allegations.
Between 300 and 400 activists had been due to set sail this week from Gaza to try to breach the naval blockade Israel imposed after anti-Israel Hamas militants overran the Palestinian territory in 2007.
It is not clear when they will set sail on their journey, which is expected to take several days.
Last year, an Israeli raid on a similar flotilla killed nine activists on a Turkish vessel, the Mavi Marmara. Each side blamed the other for the violence.