Japan's Tokyo Electric Power Company (TEPCO) on Wednesday restarted a reactor at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture despite local opposition, marking the first operated by TEPCO to go back online since the 2011 Fukushima nuclear disaster.

Reactor No. 6 at the seven-unit complex, about 220 kilometers northwest of Tokyo, began its nuclear reaction shortly after 7 p.m. local time. The utility said it received approval from the country's Nuclear Regulation Authority to conduct trial operations earlier in the day.

TEPCO initially planned to bring the reactor back online on Tuesday, but had to postpone due to an alarm malfunction during a test operation.

Despite a survey showing that residents were split over the resumption, Niigata Governor Hideyo Hanazumi gave the greenlight for plant restart last November and the prefectural assembly followed up a month later.

The Kashiwazaki-Kariwa plant, the world's biggest nuclear power station capable of producing 8.2 gigawatts of electricity when at full capacity, was among 54 reactors shut following the March 2011 core meltdowns at TEPCO's tsunami-stricken Fukushima Daiichi plant.