BERLIN (BLOOMBERG) - Germany's military is investigating what information three Chinese reporters collected while Chancellor Angela Merkel visited a North Atlantic Treaty Organisation (Nato) unit, signalling heightened mistrust of the state-run Xinhua news agency.

The Xinhua reporters raised suspicion by filming military equipment and interviewing soldiers about their daily routines, according to a person familiar with the incident who asked not to be identified discussing security matters.

They were accredited along with other journalists to enter the base and report on Mrs Merkel's visit to the Very High Readiness Joint Task Force training area at Munster, Germany, on May 20.

A German intelligence official said Xinhua has been under observation for some time due to its links to China's ruling Communist party.

German intelligence views Xinhua reporters as feeding Chinese propaganda efforts and helping collect data and information abroad that's subsequently put to official use, the official said.

The US government ordered Xinhua and broadcaster China Global Television last September to register under the Foreign Agents Registration Act.

As a result, Xinhua is required in the US to disclose activities and spending and to introduce disclaimers regarding its journalistic content.

Germany doesn't have such a classification for media organisations, though reporters are liable to prosecution if they commit a crime.