TOKYO, Sept. 25 (Xinhua) -- A Japanese high court on Tuesday revoked an injunction issued in December on appeal by Shikoku Electric Power Co. to restart a nuclear reactor in western Japan, despite ongoing safety concerns.

The Hiroshima High Court had previously demanded that the utility shut down the No. 3 unit at its Ikata power plant in Ehime Prefecture until the end of this month due to safety risks associated with potential volcanic activity.

The U-turn on the ruling by the high court follows a request made at the end of last year by a local residents group based on concerns that a volcanic eruption at Mount Aso in Kumamoto Prefecture could see heated rocks and volcanic ash reach the plant.

In the injunction, the high court had initially sided with the residents group saying that the utility had underestimated the scenario that the plant could be damaged by a major volcanic event.

But Presiding Judge Masayuki Miki was quoted as saying in the ruling Tuesday that the case of a major volcanic event occurring while the plant is operational has not been grounded in fact or science and the chances of such an occurrence happening were slim.

"The possibility of a destructive volcanic eruption during the plant's operating period is not backed by grounds and there is a small chance of volcanic ash and rocks reaching the plant, which is about 130 kilometers away," Miki said.

Shikoku Electric now plans to reboot the reactor as soon as possible and is aiming to bring it back online on Oct. 27, the utility said.

Other residents groups, however, are also planning to block the restart of the reactor and their court cases are still pending.

The groups are based in neighboring Oita, Kagawa and Yamaguchi prefectures.

The Oita District Court is expected to hand down its ruling on Friday.

The country's nuclear watchdog, based on the Hiroshima High Court's ruling Tuesday, said it will continue to ensure that the highest safety standards continue to be adhered to.

"Drawing on the lessons learned from the nuclear accident at the Fukushima Daiichi plant, we will continue to impose strict regulations based on scientific and technical knowledge," the Nuclear Regulation Authority said.