CCTV cameras have been installed after the calls made on Sunday and the SP’s security cover has been enhanced. Police said they are investigating possible terror links, but it is not clear as yet why Ayan Mukherjee (32) made the threat calls.

Police said Mukherjee called up the Golabari police station and the Shibpur police barracks on Sunday night with threats to blow up the bungalow.

“He had called from a Bankura number. During the investigation, we found he had gone to meet a relative in Bankura’s Khatra area and had made the calls from there. When we questioned his relatives there, we were told he had left for his native place in Purulia. We arrested him on Wednesday night from there,” the police said.

Mukherjee, who is unemployed, hails from Purulia but stayed at Danesh Seikh Lane in Howrah with his mother, who works at the district magistrate’s office there.

The police said his mother claimed Mukherjee is mentally disturbed, but could not back up the claim with medical documents.