According to court sources, during an in-camera hearing, District Judge Amar Nath allowed the National Investigation Agency's (NIA) plea seeking extension of the custody of the accused.
Earlier on April 21, the probe agency had told the court that the accused were involved in a larger conspiracy of the outfit, in India and abroad, including recruitment of resident and non-resident Indians. The terror group has captured vast territories in Iraq and Syria.
Those whose custody was extended are -- Mohd Aleem, Mohd Obaidullah Khan, Nafees Khan, Mohd Shareef Moinuddin Khan, Asif Ali, Najmul Huda, Mudabbir Mushtaq Shaikh, Mohd Abdul Ahad, Suhail Ahmed, Syed Mujahid, Mohd Hussain Khan, Mohd Afzal, Imran and Abu Anas.
They were arrested from different parts of the country for allegedly recruiting and financing people to join the terror organisation.
The NIA had earlier told the court that the accused, in the course of interrogation, had admitted to "their involvement in this case about recruiting and financing persons willing to join the Caliphate of ISIS at Syria".