Stricter radiation emission norms for mobile towers came into effect from Saturday, with a view to reduce emission to one-tenth of the present levels.

Failure to stick to the prescribed levels will attract a penalty of Rs 5 lakh per tower.

Radiation norms for mobile handsets have been made more stringent, but cell-phone makers have been given a year to comply with new guidelines.

Telecom Minister Kapil Sibal had on Friday said the new limits for towers were 10 times more stringent than norms followed in most parts of the world.

The Telecom Enforcement Resource and Monitoring (TERM) cells would conduct random audits. A fine of Rs 5 lakh per tower can be imposed if any operator is found lagging in meeting the prescribed levels.

Telecom Secretary R Chandrasekhar said 95 per cent of the nearly 500,000 towers in the country have already geared up to meet the new standards.

As per the new norms, mobile handsets have been prescribed with a lower specific absorption rate (SAR) of 1.6 watts/kg averaged over one gram of human tissue as compared to 2 watts/kg measured over 10 grams of human tissue at present.

All new handsets, either manufactured in the country or imported, have to follow the revised SAR levels, while one-year extension has been given to companies to phase out the existing phones which are in stock.

"Existing handsets can continue to be used or will have to be phased out during the course of next year so that September 1, 2013 all handsets used in India must comply with these norms," Sibal had said.

The new guidelines ban roof-top towers with multiple antennas and call for avoiding installing base station antennas in lanes narrower than 5 meters.