Japan has started releasing nuclear-contaminated water from the crippled Fukushima Daiichi Nuclear Power Plant into the Pacific Ocean on Thursday, while hundreds of Japanese gathered in central Tokyo to rally against the discharge plan.

Live video provided by the plant operator Tokyo Electric Power Company (TEPCO) showed that a staff member turned on a seawater pump at around 1:00 p.m. local time (0400 GMT), marking the beginning of the controversial ocean discharge, while concerns and opposition persisted among local fishermen as well as in neighboring countries and Pacific island countries.

The nuclear-contaminated water has been diluted as planned before being discharged via an underwater tunnel 1 kilometer from the plant, according to TEPCO.

Under scorching heat, hundreds of Japanese from all across the country gathered in front of the TEPCO headquarters in central Tokyo on Thursday morning, demanding the Japanese government and TEPCO to stop the ocean release.

Protesters, holding banners and placards with drawings of marine products and Godzilla, chanted slogans of "No ocean discharge of Fukushima nuclear-tainted water" and "Stop polluting the sea with radioactive water."

Taeko Fujimura with Japan's National Federation of Agricultural Cooperative Associations, also known as Zen-Noh, said the ocean discharge "cannot be forgiven" and was "extremely unreasonable."

China will suspend the imports of all aquatic products originating from Japan starting from Thursday to prevent risks from Japan's discharge of nuclear-contaminated water.

The General Administration of Customs (GAC) said in a statement that it has decided to take the emergency measures to comprehensively prevent radioactive pollution risks caused by Japan's discharge of the nuclear-contaminated water, protect the health of Chinese consumers and ensure the safety of food imports.

The decision has been made in compliance with China's food safety law, administrative protocols regarding the safety of food imports and exports, as well as the WTO's agreement concerning the application of sanitary and phytosanitary measures, according to the GAC.

South Korean Prime Minister Han Duk-soo said Thursday that the country will also keep its import ban on Japan's fishery products in place, in an address made after Japan started dumping nuclear-contaminated water into the ocean earlier in the day.

Han told a nationally televised address that the South Korean government will sternly maintain import restrictions on Japan's fishery products, stressing that the concerns among South Korean people about the easing or lifting of import restrictions on Japanese seafood will never be realized.

The prime minister noted that the import restrictions were imposed to protect South Korean people from radioactive materials following the Fukushima nuclear accident in March 2011.

Han said Japan should strictly comply with scientific standards and transparently provide information as it promised to the international community, and urged Tokyo to transparently and responsibly offer South Korea relevant information on the nuclear-contaminated water discharge that will continue for the next 30 years.

Small-scale fishers in the Philippines on Thursday slammed Japan for dumping nuclear-contaminated water into the Pacific Ocean, vowing to hold a protest rally in front of the Japanese Embassy in Manila to dramatize their protest against Japan's action.

"Japan's action pollutes the ocean, endangering the marine resources and destroying the ecosystem," said Ronnel Arambulo, the vice chair of the group PAMALAKAYA, a federation of community fishers' organization.

Arambulo said Japan repeatedly ignored the growing clamor of the people from many East Asian nations, especially the farmers and fishers, to stop the dumping of toxic nuclear-contaminated water into the world's largest ocean.

Meanwhile, the Philippines' Department of Foreign Affairs said the Southeast Asian country "continues to look at this issue from a science- and fact-based perspective and its impact on the waters in the region."

Hit by a magnitude-9.0 earthquake and an ensuing tsunami on March 11, 2011, the Fukushima plant suffered core meltdowns that released radiation, resulting in a level-7 nuclear accident, the highest on the International Nuclear and Radiological Event Scale.

The plant has been generating a massive amount of water tainted with radioactive substances from cooling down the nuclear fuel in the reactor buildings, which are now being stored in about 1,000 storage tanks.

TEPCO said it plans to carry out the first round of release over the next 17 days to discharge 7,800 tonnes of nuclear-contaminated water.

In the current fiscal year through next March, a total of 31,200 tons are slated for discharge, equivalent to the storage capacity of 30 tanks, TEPCO added.

(With input from Xinhua)