Moscow, Oct 30 (IANS/RIA Novosti): An Indian Kilo class diesel-electric submarine that has been overhauled at the Zvezdochka shipyard in northern Russia has sailed for two-week sea trials, the company said.

INS Sindhurakshak, which was handed over to the Indian Navy in 1997, has been upgraded under a direct contract between the Zvezdochka shipyard and the Indian defence ministry, signed June 4, 2010.

"The Indian submarine, which has been repaired and modernized at the Zvezdochka shipyard, sailed for sea trials on Monday," the company said in a statement.

The upgrade programme stipulated a complete overhaul of the submarine, including its hull structures, as well as improved control systems, electronic warfare systems, and an integrated weapon control system. The upgrade is reported to cost around $80 million.

The sub is expected to be delivered to India by the end of 2012, following a series of additional tests.

Russia has built ten Kilo class submarines for India and has already overhauled four of them: INS Sindhuvir, INS Sindhuratna, INS Sindhughosh, and INS Sindhuvijay.

The overhauled Indian submarines are equipped with 3M-54 Club-S (SS-N-27) anti-ship cruise missiles, the Indian-developed USHUS sonar, CCS-MK radio communications system and Porpoise radar.