TOKYO - Japan on Wednesday night restarted the No. 4 reactor at the Oi nuclear power plant in Fukui Prefecture, the second such case after Fukushima crisis put all 50 of the nation's reactors offline for regular checkups.

The retrieved 1.18 million kilowatt No. 4 reactor will begin power transmission on Saturday and start full operation on July 25.

The operator of the plant, Kansai Electric Power Co., earlier reactivated the No. 3 reactor, the first reactor after Fukushima nuclear crisis last year, on July 1, easing the government's power constraints in western Japan.

The restarts have triggered street protests, with more than 100,000 people walking through downtown Tokyo on Monday to condemn atomic energy.

The No. 4 reactor was shut on July 22 last year for maintenance.