Japan on Thursday began releasing a second batch of treated radioactive wastewater from the wrecked Fukushima nuclear power plant, into the ocean.

The discharge began at 10:18 am (0118 GMT), the plant's operator, Tokyo Electric Power Company Holdings (TEPCO), told news agencies.

TEPCO said that its workers activated a pump to dilute the treated water with large amounts of seawater, slowly sending the mixture, through an underground tunnel, into the sea.

The first discharge of wastewater from the plant  — which was struck by a devastating tsunami in 2011 — began on August 24 and ended on September 11. A total of  7,800 tons of treated water from 10 tanks was discharged during that release, TEPCO said.

The plant plans to release another 7,800 tons of treated water into the Pacific Ocean over 17 days in the second phase.

'Safe' first release

Since the disaster, around 1.34 million tons of radioactive wastewater has been stored in about 1,000 tanks at the plant.

"It has been confirmed that the first release has been conducted as planned and in a safe manner," government spokesman Hirokazu Matsuno told the media on Thursday, emphasizing that no abnormalities had been detected. 

The government will "continue to communicate, both domestically and internationally, results of monitoring data in a highly transparent manner," Matsuno added. 

The spokesperson also said that Tokyo will call on China — which has imposed restrictions on Japanese seafood shipments —  to "immediately scrap import bans on Japanese food, and act based on scientific justifications".

dvv/kb (AFP, AP)