India, July 10 -- No app can block phone calls originating from 1600 number series that are meant for communications by regulated entities and the government to citizens, the Telecom Regulatory Authority of India (TRAI) said in a statement on Friday. The authority also clarified that promotional calls originating from 140 number series cannot be tagged or filtered by an app, and can be blocked only by the DND registry managed by the regulator itself.

"Under the Telecom Commercial Communications Customer Preference Regulation (TCCCPR), any tagging, blocking or filtering of the calls originating from 1600 series numbers is not permitted," Trai said.

The key objective of assigning designated series 1600 for important communications is to m...