TOKYO — The operator of Japan’s tsunami-hit nuclear power plant sounded the alarm on the gravity of the deepening crisis of containment at the coastal site on Friday, saying that there are more than 200,000 tons of radioactive water in makeshift tanks vulnerable to leaks, with no reliable way to check on them or anywhere to transfer the water.

The latest disclosures add to a long list of recent accidents, leaks and breakdowns that have underscored grave vulnerabilities at the Fukushima Daiichi nuclear power plant site more than two years after a powerful earthquake and tsunami set off meltdowns at three reactors.

They come two weeks after the prime minister, Shinzo Abe, promised that his government would take a more active role in the site’s cleanup, raising questions over how seriously he has taken that pledge. Mr. Abe’s government has continued to push for a restart of the country’s nuclear power program, and he heads to the Middle East on Saturday to promote Japanese exports to the region, including nuclear technology.

Mr. Abe also plans to lead Tokyo’s delegation to Argentina for the International Olympic Committee’s final vote, set for Sept. 7, on the host city for the 2020 Olympics. Tokyo, 150 miles south of the stricken nuclear power plant, is one of three finalists competing to host the games. The others are Istanbul and Madrid.