Hackers in support of Turkish President Recep Tayyip Erdogan have hijacked a number of high-profile Twitter accounts and defaced them with Nazi slurs.
Justin Bieber's Japanese account was among those targeted, as were accounts belonging to Forbes, Blockchain, Britain's Department of Health and German soccer club Borussia Dortmund.
The message began with the hashtages '#Nazialmanya' (Nazi Germany) and 'Nazihollanda' (Nazi Holland), an apparent reference to the diplomatic row which has developed between Germany and the central European countries in recent days.
The message continued: "This is a small #Ottomanslap for you. See you on #April16 [for the Turkish referendum]. I wrote what? Learn Turkish."
Twitter confirmed there had been an attack on Wednesday morning.
The company explained they had removed the privileges from the source of the attack - a third-party app.
Mr Erdogan has launched Nazi slurs at both Germany and Holland in recent days, after his ministers were prevented from speaking in the two countries.
The Turkish president is seeking a range of new powers in next month's referendum, and is targeting votes from the country's diaspora to swing the vote his way.