Japan hopes to restart four more nuclear reactors in time to avert any power crunch over the winter, industry minister Koichi Hagiuda said on Friday, a week after the pro-nuclear ruling party won a resounding victory in upper house elections.

"We would like to ensure the operation of a maximum of nine reactors, up from the current five operating now, by revising the construction and inspection periods for some of the nuclear power plants," Hagiuda told a news conference.

Many of Japan's nuclear reactors remain idled after a massive tsunami triggered a disaster at the Fukushima Daiichi nuclear power plant in 2011, but the ruling Liberal Democratic Party (LDP) has been eyeing a return to nuclear power as a stable source of energy for resource-poor Japan.

Public opinion had broadly opposed nuclear restarts following the Fukushima disaster, but the tide has shifted given rising fuel prices and bouts of unseasonable weather that have triggered calls for energy-saving.

A nuclear restart still requires an extensive approval process overseen by regulators, as well as approval from local communities.

Flaring tensions with Russia have also put Japan on edge.

A decree issued by President Vladimir Putin in late June that seizes control of gas and oil project Sakhalin-2 has threatened to cut off a crucial source of gas supplies for Japan.

Gas Association chairman Takehiro Honjo said on Friday there were no immediate concerns over the supply of gas.

Sakhalin-2 supplies 9% of Japan's liquefied natural gas.

(Reporting by Sakura Murakami; Editing by Jacqueline Wong & Simon Cameron-Moore)