KOLKATA (AFP) Upul Tharanga cracked a robust century to help Sri Lanka post a challenging 315-6 against India in the fourth one-day international that was interrupted by a power outage on Thursday. The left-handed opener hit two sixes and 14 fours in a 128-ball 118 for his seventh one-day hundred to keep alive his teams hopes of squaring the five-match series. The visitors trail 2-1 following their defeat in the previous game. Sri Lanka were 307-6 in 49.2 overs when play was held up for 23 minutes in the day-night match due to a power failure in one of the light towers at the Eden Gardens. Tharanga propped up the innings after the early dismissals of in-form opener Tillakaratne Dilshan (nine) and Sanath Jayasuriya (15), adding 126 for the third wicket with skipper Kumar Sangakkara (60). But there was no stopping Tharanga, who dominated the Indian attack with a wide range of strokes. He severely punished paceman Ishant Sharma, hammering five fours in an over. Sri Lanka plundered 98 in the last 10 overs, with debutant Thissara Perera smashing a 14-ball 31 and Mahela Jayawardene 33 in 30 deliveries. Tharanga offered a difficult chance on seven when Nehra failed to hold a firmly-struck shot off his own bowling. He then gave no hope to the Indians, scoring comfortably against both pace and spin. Sangakkara, dropped by Harbhajan Singh off Sharma before he had opened his account, made the most the opportunity as he consolidated his teams position with a big stand with Tharanga. The Sri Lankan skipper fell in a bid to step up the rate-rate, stumped by Dinesh Karthik off Harbhajan after hitting five fours. India, who are without hard-hitting batsmen Mahendra Singh Dhoni and Yuvraj Singh, need to put in an impressive batting performance to clinch the series. Dhoni is serving a two-match ban for a slow over-rate during his teams defeat in the second match in Nagpur, while Yuvraj has been ruled out of the last two games due to a finger injury.