German Chancellor Angela Merkel on Sunday opens a major IT business fair where official partner China will showcase its rise as a high-tech power.

Merkel -- who has visited China seven times in a decade -- will meet Vice Premier Ma Kai as more than 600 Chinese companies exhibit their tech marvels at the CeBIT fair in the western city of Hanover.

Jack Ma, head of Alibaba -- the online commerce giant that is China's answer to eBay and Amazon -- will give the keynote address, and companies including Huawei, Xiaomi and Lenovo will fill over 3,000 square metres (30,000 square feet) of exhibition space.

China's huge showing "makes it the biggest and strongest partner country presentation we've ever seen at CeBIT," said top exhibition executive Oliver Frese.

Bucking China's wider economic slowdown, information and communication technology are booming in the world's biggest smartphone market with the highest number of Internet users.

"China was known as a supplier of components and later as a supplier of hardware, smartphones, tablets and also PCs," said CeBIT spokesman Hartwig von Sass.

"Now China has numerous companies that have become world leaders ... for example Huawei, ZTE, Neusoft or Alibaba, some of which are far bigger than western IT companies.

"We see this as a shift on the world map: digitisation is going east."

- Industry 4.0 -

The almost three-decade old CeBIT once dazzled consumers with gadgets but has been overshadowed by big tech events in Las Vegas and Barcelona, leading it to focus on business users.

Last year IT professionals made up more than 90 percent of the over 200,000 visitors.

For Germany, the event aims to further cement economic ties with fellow export power China as both seek to adapt to the sweeping digitisation of the world economy.

Germany calls it "Industry 4.0" -- the fourth industrial revolution after steam power, factory mass production and the dawn of electronics and IT.

It refers to connecting automated manufacturing with the online world and the "Internet of Things", where everything from factories, homes and cars to household appliances will be online.

In October China's Premier Li Keqiang praised the "innovation partnership" with Germany and said his country must better harness the creative talents of its 1.3 billion people.

Germany is already by far the biggest European economic player in China, and its exports there have helped it offset the impact of the financial crisis in Europe. Two-way trade last year topped 140 billion euros ($177 billion).

Jost Wuebbeke of the Mercator Institute for China Studies said "the Chinese IT market will grow rapidly in future and have great influence on the global market".

In China-Germany trade, IT still plays a minor role, he said, predicting however that it "could become far more important through German-Chinese cooperation in the field of Industry 4.0".

- 'Firewall of China' -

The choice of the Asian giant as partner country however throws a spotlight on its huge Internet surveillance system dubbed the "Great Firewall of China".

Human rights group Amnesty International plans to protest during CeBIT against China's treatment of critics, including jailed Nobel Prize laureate Liu Xiaobo.

Merkel still speaks out on human rights but has been mindful to avoid major offence since she angered Beijing by receiving Tibetan spiritual leader the Dalai Lama in 2007.

"The German government must ask itself how it will contribute to improving the human rights situation in China," said Amnesty's Verena Harpe.

Berlin and Beijing have been holding joint cabinet meetings every two years -- a format that is unique for China and which Germany has with only a few other countries, among them France, Israel and India.

Some analysts worry that Germany's increasingly close ties with China could become problematic as the Asian giant grows more assertive in its region and on the world stage.

"The relationship between China and Germany has shifted and will continue to shift from a purely economic relationship to security issues," said Hans Kundnani of the European Council on Foreign Relations.

"On the one hand it is an opportunity. Germany certainly has more access in Beijing and more leverage than any other EU member state, but there is also a danger," he told AFP.

"The worry would be that Germany develops a privileged relationship with China on security as well.

"As tensions increase between China and its neighbours ... you could have a situation where Germany undermines a coherent European approach on security issues in Asia."