Bengaluru, Dec 18 (IANS): A court here Thursday extended the police custody of alleged Islamic State (IS) supporter Mehdi Masroor Biswas by 15 days for further interrogation on charges of waging war against a country which is at peace with India, police said.

"We produced Mehdi in the sessions court on expiry of his five-day custody to further interrogate him on his postings in the social media and Twitter handle (@ShamiWitness), as part of our investigation. We have secured his custody for another 15 days up to Jan 2," city police commissioner M.N. Reddi told reporters.

Police registered a criminal case Dec 13 against Biswas under specific sections of the Indian Penal Code (IPC), the Unlawful Activities (Prevention) Act and the Information Technology (IT) Act for waging war against any Asiatic power in alliance or at peace with India.

A British news channel Dec 11 unmasked the city-based 24-year-old executive as a radical supporter of the IS through social media and Twitter.

"The investigation so far has revealed that Biswas is a propagandist of IS ideology and has been instrumental in influencing minds against our friendly countries and against whom the terror group is at war," Reddi said.

Biswas, who hails from Gopalpur town in West Bengal's Nadia district, is employed in the foods division of a Kolkata-based company in Bengaluru.

He confessed that he was operating the Twitter account after he got interested in the developments of the Levantine region comprising Turkey, Syria, Lebanon, Israel, Gaza Strip, Egypt and Libya.

His parents - Mikhael Biswas and Mamtaz Begum - who arrived in Bengaluru Wednesday from Kolkata, were allowed to meet their son at an undisclosed place, as he has been in police custody since Dec 14.

"His parents also met me and shared their concerns over his alleged involvement with the IS terror activities through the social media. I have assured them that our investigation would be impartial, unbiased and objective," Reddi said.