Israeli forces took command of the charity vessel that had tried to break a naval blockade of the Gaza Strip and has detained its crew as it is steered to a port in Israel, officials said.
"If you see this video we have been intercepted and kidnapped in international waters," she said.
In another pre-recorded message, Brazilian activist Thiago Ávila called for support for him and the other members of the flotilla who have been detained.
Freedom Flotilla organiser Huwaida Arraf said Israel did not have any authority to detain the volunteers who were aboard the ship.
"Their detention is arbitrary, unlawful, and must end immediately," she said.