Sistema is planning to increase its stake in Shyam Telelink to 72 per cent. The Russian company had bought a 51 per cent stake in Shyam and entered into a call option that potentially allowed it to boost its stake to 74 per cent over a defined period of time.

Sistema has now signed an amendment to the call option which gives it the right to accelerate the purchase of an additional 21 per cent stake for $45 million at any time.