A team of South Korean experts has started a four-day survey in Japan to check on the safety of treated and diluted water from the crippled Fukushima Daiichi nuclear power plant that is slated to be released into the sea.

Under the government plan, the treated water from the plant will be diluted to reduce tritium levels to meet World Health Organization safety standards for drinking water before it is released into the ocean.

Tokyo Electric Power Company, the operator of the plant, is making preparations for a first release around this summer.

The Japanese and South Korean leaders agreed at their summit on May 7 that Seoul would send experts for an on-site survey in Japan.

The team of about 30 includes senior officials of the country's Nuclear Safety and Security Commission and marine environment experts. They arrived in Japan on Sunday and will stay through Friday.

Sources say the team held talks with Japanese government officials on Monday. The officials reportedly told the team about progress of construction work needed to facilitate the release.

The team will make a two-day visit to the plant starting Tuesday to examine how the treated water is stored and see an analysis of data on the water.

Concerns are being voiced in South Korea about the release of the treated and diluted water.

Tokyo wants to use this occasion and any other opportunity it gets to convince Seoul that the plan ensures the safety of such a release.

Seoul says the team was sent to understand how released water would impact South Korea's territorial waters and fisheries products. It says it will promptly take necessary measures based on the team's findings.

South Korea currently bans certain fisheries products from Fukushima and several other prefectures due to safety concerns over radioactive contamination.