German Chancellor Angela Merkel has urged closer high-tech cooperation with China as she opened major IT business fair CeBIT, for which China is the official partner country.

"German business values China, not just as our most important trade partner outside of Europe, but also as a partner in developing sophisticated technologies," Merkel said.

"Especially in the digital economy, German and Chinese companies have core strengths ... and that's why cooperation is a natural choice."

Merkel was speaking at the opening of the CeBIT fair in Hanover, Germany, where more than 600 Chinese companies will exhibit their tech marvels this week, showcasing the country's rise as an IT power.

China's information and communications technology has bucked the country's wider slowdown in economic growth, and is booming in what is now the world's biggest smartphone market with the highest number of internet users.

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

Germany is already by far the biggest European economic player in China; two-way trade in 2014 reached €150 billion. Both countries have declared 2015 the year of their "innovation partnership".

The almost three-decade-old CeBIT once dazzled consumers with gadgets, but has been overshadowed by big tech events in CES in Las Vegas and MWC in Barcelona, leading it to focus on business users. Last year, IT professionals made up more than 90 percent of the more than 200,000 visitors.

China's tech giants, including Huawei, Xiaomi, and Lenovo, filled more than 3,000 square metres of exhibition space.

AAP