"We are very much counting on starting mass production in September," an official said.

Greenpeace Russia said an area greater than the size of Portugal has been impacted by the fires.

Had the company replaced the old reservoir, it would not be faced with such expenses now, Putin said.

"There haven't been such spills in the Arctic before."

Putin's bonus promise sounded promising but has "resulted in huge disappointment among doctors," medics say.