A reactor at the trouble-hit Genkai nuclear power station in Saga Prefecture was restarted Saturday for the first time in more than 6½ years despite lingering safety concerns.

The No. 4 unit at the Genkai plant is Kyushu Electric Power Co.'s fourth, and the nation's ninth, to go back online since stricter safety rules were adopted following the 2011 Fukushima nuclear crisis.

The utility aims to generate and supply electricity starting Wednesday, before resuming commercial operations in mid-July.