Japan’s government on Monday told the operator of the crippled Fukushima nuclear plant to move quickly to stop radiation seeping into the ocean.

Officials grappling to end the world’s worst nuclear crisis since Chernobyl tried to seal a crack that has been leaking radiation into the sea.

Japan’s nuclear and humanitarian crisis stretched to three weeks on Friday with radiation still leaking from a crippled nuclear power plant.

Japan made some progress to avert disaster at a tsunami-damaged power plant, though leaks underlined perils from the worst crisis since Chernobyl.

China told Japan on Tuesday to stop interfering with Chinese fishery protection vessels operating in seas claimed by both countries.