(Adds Chinese ministry comment)
GENEVA, Feb 13 (Reuters) - A World Trade Organization dispute panel upheld most parts of a complaint against China on Friday in a case brought by Japan and the European Union challenging Chinese anti-dumping duties on high performance seamless stainless steel tubes.
Japan brought the complaint in December 2012 to object to China hampering firms such as Nippon Steel & Sumitomo Metal Corp from selling the tubes, which are used in coal-fired power plants.
The European Union, home to exporters such as Tubacex S.A in Spain and Salzgitter A.G in Germany, joined the case against China in June 2013.
"In international trade we all need to play by the rules. I am glad that the WTO panel confirms this today asking China to bring its customs duties in line with the WTO obligations," EU Trade Commissioner Cecilia Malmström said in a statement.
"I hope to see China reacting to this ruling immediately and restoring fair trading conditions for EU producers."
The EU said the ruling was of systemic importance because it highlighted "recurrent shortcomings" in China's application of the trade rules, following another dispute where the EU challenged Chinese anti-dumping duties on x-ray scanners.
WTO rules allow countries to apply anti-dumping duties against unfairly priced imports, but there are strict conditions about applying the rules and calculating whether the goods are actually being dumped.
China, which could appeal against the ruling, said it had several objections to the findings but did not immediately say what it would do next.
"We will earnestly assess the report and consider possible future steps," China's Ministry of Commerce said in a statement on Saturday.
China is also under new pressure from the United States, which launched a new complaint at the WTO on Wednesday to challenge Chinese subsidies supporting billions of dollars of exports.
Canada has also escalated a trade row with China by asking the WTO to adjudicate in a dispute about China's anti-dumping duties on cellulose pulp, used to make rayon. (Reporting by Tom Miles; Additional reporting by Gerry Shih in BEIJING; editing by Stephanie Nebehay)