A BBC crew was detained and their video footage confiscated by the Chinese military during its investigations into a secretive cyber espionage group.

Beijing correspondent John Elsworthy was among those detained by military personnel following the publication of a report by US cyber security firm Mandiant claiming to have pinpointed the home of the cyber warfare unit at a “non-descript” complex in Shanghai.

Elsworthy and his crew were stopped “pretty promptly from filming” outside building, which was said to house one of the world's "most prolific cyber espionage groups", Unit 61398.

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“We were stopped pretty promptly from filming,” Elsworthy told the BBC. “We were briefly detained by the military personnel on the gates, taken inside the base and they refused to let us go until we had agreed to surrender our tape.

“The Reuters news agencies were able to pick up some footage, and you can see form those pictures that this is a pretty nondescript building.

“Certainly it doesn’t look likely to be the nerve centre of one of the most effective and prolific cyber warfare operations ever mounted…”

According to Mandiant, Unit 61398 has “systematically stolen hundreds of terabytes of data" from at least 141 organisations around the world.

In recent weeks both the Washington Post and New York Times claim to have be subject to hacking attacks emanating from China.