India's leading mobile operator Bharti Airtel on Monday slashed STD and roaming tariffs by up to 43 per cent benefiting its 62 million customers and starting a new price war in this segment after local calls. The company has reduced STD rates by 43.39 per cent to Re 1.50 minute from the earlier Re 2.65 per minute. The new tariffs would be effective from April 30 and would be available for both pre and post-paid users.