Telecom regulator TRAI on Monday allowed ISPs to offer unrestricted internet telephony services, a move that will further boost competition in the domestic long distance segment and lower STD tariffs.

"It is envisaged that customers will ultimately benefit from cost effective and innovative internet telephony service. These recommendations will put Indian telecom sector in tune with global trends. The grey market tendencies shall be curtailed," TRAI said in a statement.

As per the TRAI recommendations, the STD service providers would be connected to ISPs through public internet for the purpose and the two service providers would have mutual agreement for the same.

The move will permit calls from personal computers to fixed line and mobile phones. Currently, a voice call can travel between two computers but not from a mobile or a fixed phone. This is expected to open huge channels of revenues for Internet Service Providers (ISPs).

The Telecom Engineering Centre (TEC), a technical arm of Department of Telecom, will work out the number plan for the ISPs to enable them to offer telephone services.

"Telephone numbers from identified blocks shall be allocated to ISPs, Unified Access Service Providers, Basic Service Providers and Cellular Mobile Service Providers for internet telephony," TRAI said.

With a view to make internet telephony secure, TRAI said, all ISPs interested to provide unrestricted internet telephony would install "Lawful Interception" equipments.