South Korea's nuclear safety watchdog said it sent an inquiry to its Japanese counterpart regarding details of Japan's planned release of radioactive water into the ocean and the agency's review process.

The Nuclear Safety and Security Commission said on Tuesday that it sought information on the sustainable verification of Japan's extensive filtering procedure known as the Advanced Liquid Processing System(ALPS).

It also asked for information on the monitoring of the water treatment and disposal, and plans for further verification by a third party.

The South Korean watchdog earlier expressed deep concern over Japan's decision, while demanding an objective and autonomous review of the plan and the prompt and transparent sharing of information.