India sets Blackberry monitoring deadline

The move will increase pressure on Blackberry maker Research in Motion (RIM) to allow Indian security agencies access to encrypted messages.

Tata Teleservices told BBC News that the letter said it must "ensure that Legal Intervention (LI) capability is put in place" by the end of the month.

RIM said it grants "lawful" access.

A spokesperson for Tata Teleservices said: "As a Tata Group company, we have always abided by the law of the land and will do so here too".

Other operators have confirmed that they received a similar request.

The government has said it will shut down Blackberry services if the firm does not meet its demands to give access to its encrypted messenger and e-mail services by 31 August.

In statement released on 12 August, the government said that other Blackberry services, including voice and SMS traffic, were already "available to law enforcement agencies".

India, along with many other countries, believes the device and the Blackberry infrastructure are a threat to national security.

Blackberry handsets automatically scramble messages and send them to servers in Canada and other countries.

Authorities have said they want access to these messages and the keys to decrypt them to counter terrorism and criminal activity.

The row in India is the latest in a long-running dispute between RIM and international governments.

See www.bbc.co.uk for full version.