ISTANBUL (Reuters) - Flag carrier Turkish Airlines said on Friday it was assisting an investigation into three British schoolgirls believed to have gone to Syria to join Islamic State in Iraq and Syria (ISIS).

"Turkish Airlines is assisting the relevant government bodies in their inquiries but is unable to respond to or comment specifically in relation to the subject matter of ongoing investigations," it said in an e-mailed statement.

British police said this week they believed friends Amira Abase, 15; Shamima Begum, 15; and Kadiza Sultana, 16, had crossed into Syria after flying to Istanbul from London on Feb. 17.