More than 25 million Indian phone users have had their gear blocked in a bid to tighten security in the continent.

The Chinese-made mobile phones do not have an identification number allowing calls to be traced. Coms companies have been told to refuse calls that do not have a 15-digit International Mobile Equipment Identification (IMEI) number. The IMEI number helps identify all calls received and made on a phone and provides information on the manufacturer and type of handset. The IMEI is automatically registered with service providers when they are first activated.

Users can manually register their phone with their service provider and buy an IMEI for 199 rupees ($4). The main problem is that the phones are cheap and popular in India and there could be a lot of people miffed that their phones have been switched off.

The Indians are not big fans of Chinese gear. India's intelligence agencies have warned that Chinese products could have embedded elements enabling China to launch a cyber attack or shut down the equipment. There are more than 500 million mobile users in India.