German Chancellor Angela Merkel on Wednesday accused China of "poor and cruel treatment" of minorities and underlined deep concerns over the crackdown on dissent in Hong Kong.

In a speech at the Bundestag a day before an EU summit, Merkel vowed to bring up rights issues and Germany's worries over the situation in the former British colony in any future dialogue with Beijing.

"Of course we have to bring up our different opinions in talks," said Merkel, whose country currently holds the rotating presidency of the European Union.

"That's why we have flagged up our deep concern about the development in Hong Kong. The principle of one country, two systems stands but again and again it's being undermined. We will bring that up, as well as the poor and cruel treatment in part of the rights of the minorities in China."

She did not name the minorities bearing the brunt of poor treatment but activists have accused China over the mass internment of Uighur Muslims in Xinjiang. More than one million ethnic Uighurs and other minorities have been herded into internment camps to undergo political indoctrination, according to rights groups and experts.

China insists the camps are training centres aimed at providing education to reduce the allure of Islamic radicalism. Beijing is also under fire over a security law it imposed on Hong Kong in June that radically increased its control over the financial hub and led to a brutal crackdown on dissent.

Hong Kong was guaranteed autonomy under the "One Country, Two Systems" deal agreed ahead of its 1997 handover from Britain. But critics say the security law, imposed following months of large and often violent protests calling for greater democratic freedoms and police accountability, spells the end of the agreement.

With China a key market for Germany's exporters, Berlin has sought to maintain strong ties with the Asian giant. Activists have repeatedly urged Germany for more support. During a visit by China's foreign minister to Berlin, demonstrators including Hong Kong dissident Nathan Law protested outside the German foreign ministry demanding more action.

Artist Ai Weiwei has also accused German leaders of being "so shy" in their dealings with Berlin on rights issues.

"Germany... when they're dealing with China, they've been too humble or too shy," he told journalists on Tuesday.