UPDATE 1-Man who triggered alert at UK's Buckingham Palace had a key ring-police

A man, who sparked an alert at the visitors' entrance to Queen Elizabeth's Buckingham Palace residence on Sunday when he was arrested for being in possession of stun gun, in fact just had a key ring, London's Metropolitan Police said.

The 38-year-old old tourist from the Netherlands was detained at the palace on Sunday lunchtime after he was found with a "Taser-type device" but was released without charge a few hours later.

"Officers were satisfied that his possession of the device - which was low-powered and part of a key ring – was a genuine error on his part and that he posed no threat," police said.

Parts of the palace are open to visitors for 10 weeks each year and the queen is currently on holiday in Scotland.