Austrian police arrested a Bosnian man on Monday after he tried to enter the U.S. embassy in Vienna carrying a rucksack with explosives, a police spokeswoman said.
The man ran away from the embassy after his rucksack triggered metal detectors at the entrance. He dropped the bag in the next street and was arrested shortly after, she said.
Bomb squad specialists found two devices similar to hand grenades and other explosive material in the rucksack, as well as nails and a book that had "some reference to Islam", the spokeswoman added.
The man is currently being questioned.
"He appears to be a bit confused," the spokewoman said, adding that there were no initial indications he had an Islamist background.
Austria last month arrested three people with links to al Qaeda on suspicion of posting an Islamist video on the Internet in which they threatened Germany and Austria. One of three was later released without charge.
Police said they had found no evidence that an attack was in the offing.