Japan said Tuesday it has lodged a formal protest against China's seizure of a Japanese ship over unpaid bills dating back to the 1930s, the latest row to underscore their bitter enmity.

Authorities in Shanghai said Saturday they had impounded the large freight vessel owned by Japanese shipping giant Mitsui O.S.K. Lines in a dispute over what the Chinese side says is money owed from before World War II, when Japan occupied large swathes of its neighbour.

The two sides are also embroiled in a territorial dispute over a small archipelago, as well as snapping at each other over differing interpretations of history.

On Tuesday some Japanese media suggested the ship's seizure was meant to underline China's assertiveness before US President Barack Obama's arrival in Tokyo on Wednesday, part of an Asian tour aimed at reinforcing Washington's regional security alliances.

"We have told the Chinese side through diplomatic channels that we regret its seizure of the vessel... we demand China take appropriate measures," said Chief Cabinet Secretary Yoshihide Suga, the government's top spokesman.

The ruling could "intimidate Japanese companies doing business in China", Suga said, adding that Japan was "deeply worried".

Tokyo's position is that the seizure undermines a 1972 joint communique that normalised ties between Japan and China, in which Beijing agreed to renounce any demands for war reparations.

Prime Minister Shinzo Abe described the Chinese move as "regrettable" and said that "we are demanding China take appropriate measures", Jiji Press reported.

"What's important is to observe the spirit of the rule of law," Abe said, referring to the 1972 pact.

China on Monday said the civil case had nothing to do with the kind of claims outlined in that agreement.

On Saturday the Shanghai Maritime Court said it had seized the vessel "for enforcement of an effective judgement" made in December 2007.

Chinese and Hong Kong media said the seizure was related to a verdict by a court in Shanghai that said Mitsui must pay around 2.9 billion yen ($28 million) in relation to the leasing of two ships nearly 80 years ago.

Reports said that in 1936, Mitsui's predecessor rented two ships on a one-year contract from Zhongwei Shipping Co.

The ships were reportedly commandeered by the Imperial Japanese Navy and were sunk during World War II.

A compensation suit was brought against Mitsui by the descendants of the founder of Zhongwei Shipping, and in 2007 a Shanghai court ordered Mitsui to pay compensation.

China's Supreme People's Court later rejected the Japanese firm's appeal against the judgement.

The ship seizure comes as a set of lawsuits related to wartime forced labour have also been filed in China against Japanese corporations.