A nuclear missile tracking ship India is working on is undergoing harbour trials and its manufacturer is set to deliver it by December, The Economic Times reported on Thursday. The secretive project to build the ocean surveillance ship began over four years ago. The ship will become part of an elaborate missile shield against attacks, said the newspaper.

“We have as of now finished the basin trials,” Rear Admiral LV Sarath Babu, chairman and managing director of Hindustan Shipyard Limited, which is working on the project, told The Economic Times. “We expect to deliver the ship by December this year.”

In the next step, a joint team of the Indian Navy and the National Technical Research Organisation will conduct sea trials to test surveillance systems, before the ship will be handed over to the Navy.

“The keel of the vessel was laid in June 2014 and we would have completed it in less than five years,” Babu was quoted as saying. “It is a very complex vessel and we have set a new standard for building vessels of such class on time.”

The ship, called VC11184, weighs over 15,000 tonnes and will cost Rs 725 crore. Its initial construction was done in a covered dry dock at the shipyard to prevent attempts to spy on it, the newspaper said. The vessel is said to be one of the largest warships built at an Indian yard.