Unexploded Second World War bombs at an Austrian airfield threaten to shut down a May concert by metal rockers AC/DC.

The concert at Wels Airport on May 22nd has already faced another obstacle — complaints by environmentalists that it would disturb colonies of rare birds in the area.

Now, city officials have informed the metal band that the bombs pose a danger to the estimated 80,000 fans who have bought tickets to the sold-out concert.

Hermann Wimmer, the mayor of Wels, told Austrian TV this week that approval for the concert will not go ahead until experts in demining and bomb defusing evaluate the site.

The airport had been the target of heavy Allied bombing during the war.

Earlier the rockers had sidestepped the rare-birds controversy by meeting with Austrian environmental and bird protection groups about their concert. The airport has the second-biggest colony of curlews in that province and also 200 pairs of endangered birds that nest there.

Concert organizers agreed to keep light and sound to a minimum and to stay away from 90 per cent of the airfield.

An ecological audit will also occur before and after the concert.