The ship was intercepted in international waters at 02:00 in the morning, Swedish time. The twelve activists on board, including Swedish Greta Thunberg, are to be sent back to their home countries, according to Israel.
"The Israeli forces' intervention against the ship 'Madleen' in international waters is an obvious breach of international law", says the Turkish government in a statement and calls the act a "heinous attack".
Two of the activists are said to have Turkish passports. A source at the Turkish Foreign Ministry tells AFP that the ship is expected to reach Israel "in the evening" and that consular staff will be on site to "ensure their release". Turkey is reported to be in contact with other countries that have citizens on board.
The incident occurs shortly after the anniversary of Israel's boarding of the Turkish ship Marmara, which was part of a Gaza convoy in 2010. Then, 10 Turkish citizens were killed.