Russia's state environmental watchdog said Monday that metals giant Norilsk Nickel should pay $2 billion in damages over a huge Arctic fuel spill. Rosprirodnadzor said it had sent a request for "voluntary compensation" to a subsidiary of Norilsk Nickel, NTEK, estimating the damage to Arctic subsoil and water resources at 147.8 billion rubles. Norilsk Nickel's Moscow-listed shares fell by nearly 5 percent after the statement. The company is controlled by Russia's richest man Vladimir Potanin whose fortune is estimated by Forbes at $23.5 billion. A Norilsk Nickel spokeswoman said the company had not yet received the papers from Rosprirodnadzor. A national-level state of emergency was announced after 21,000 tonnes of diesel fuel spilled from a reservoir that collapsed in May outside the Arctic city of Norilsk, polluting huge stretches of river in remote tundra with bright red patches visible from space. President Vladimir Putin has said he expected Norilsk Nickel to fully restore the environment. Potanin had earlier estimated that the clean-up would cost about 10 billion rubles, on top of any fines. "We will spend whatever is needed," he said. as/jh