Japan threatened on Tuesday to take China to the World Trade Organization to seek a reversal of Beijing's ban on all of its seafood imports after the release of treated radioactive water from the stricken Fukushima Daiichi nuclear power plant.

Japan's foreign minister Yoshimasa Hayashi told reporters that Japan will take "necessary action (on China's aquatic product ban) under various routes including the WTO framework".

Filing a WTO complaint might become an option if protesting to China through diplomatic routes is ineffective, economic security minister Sanae Takaichi said separately.

The comments came as Japanese businesses and public facilities continued to receive harassment calls from phone numbers with the +86 Chinese country code, with many reporting callers complaining of the Fukushima water release.

Japan's National Policy Agency has received 225 reports of harassment calls to date, Jiji news reported, and the government said it was seeking help from telecommunications companies to block the calls.

An increasing number of landline phone users are requesting to block foreign numbers, said a spokesperson at NTT Communications, a Nippon Telegraph and Telephone unit. NTT and other phone companies including KDDI and SoftBank Corp are discussing measures following the government’s request.

"It is extremely regrettable and concerning about the large number of harassment calls that have likely come from China," Trade minister Yasutoshi Nishimura said during a news conference. He said that according to the people of Fukushima some calls were even going to hospitals, .

"Human life is at stake now. Please stop the calls immediately,” Nishimura said.

The minister said the government is gathering information on the reports of movements to boycott Japanese products in China and would work with business leaders to address the situation.

(Reporting by Chang-Ran Kim, Kantaro Komiya and Mariko Katsumura; Editing by Simon Cameron-Moore)