VIENNA (Reuters) - Austrian anti-terrorism investigators found detailed plans of a North African embassy with notes on its security gaps during a raid last year and may have foiled an attack, officials said Wednesday.

The raid has only now been made public as the Federal Constitutional Protection and Anti-Terrorism Agency presented its annual report on security threats in Austria.

The agency's head said the Vienna embassy which he declined to identify had been immediately informed and extra protection assigned while it beefed up its own security.

"These measures (the raid) may at least have prevented the planning of an attack," Gert-Rene Polli told Reuters.

The 2003 report said there was no evidence of a direct threat to Austria, but that a latent threat hung over all of Europe and the danger of Islamic militant attacks was growing.

Investigators found the embassy drawings while serving a search warrant on suspects from North Africa, who left the country before prosecutors could take up the case.

Polli said the leads generated by the raid were more important than the fact no one was tried.