It will be a direct deal between the two governments, and will involve a payment of 150 million US dollars as a loan.
The ship will also have a helicopter pad, and Sri Lanka will be given the training and weaponry required.
The Moscow-based Rosoboronexport, a state-private enterprise, has been a key weapons seller for Sri Lanka.
Its local agent was one Priyantha, a relative of Rajapaksa-family friend Chandima Rasaputra, who died recently and his son Akila has now taken over the reins.
Akila is reportedly trying to become the local agent for the purchase of the warship from Russia.