The mass shooting at an Istanbul nightclub on New Year's Eve was carried out professionally with the involvement of an intelligence organisation, Turkish Deputy Prime Minister Numan Kurtulmus says.
"It appears the Reina attack is not just a terrorist organisation's act, but there was also an intelligence organisation involved. It was an extremely planned and organised act," Mr Kurtulmus said during an interview with broadcaster A Haber on Monday.
Islamic State has claimed responsibility for the attack in which 39 people were killed and almost 70 people were injured.
The extremists said it was revenge for Turkish military involvement in Syria.