The Swiss army is not renowned for its aggressive expeditionary adventures - but it does appear to have accidentally invaded Liechtenstein.

According to the Swiss daily Blick, around 170 infantry soldiers from the famously neutral country wandered more than a mile across the unmarked border with the tiny principality.

The incident happened yesterday morning and the Swiss troops turned back - probably slightly sheepishly - after they realised their mistake.

A spokesman for the Swiss army confirmed the story, but said that there were unlikely to be any serious repercussions for the mistaken invasion, the Associated Press reported.

"We've spoken to the authorities in Liechtenstein and it's not a problem," spokesman Daniel Reist said.

As well as the obligatory Swiss army knives, the troops were armed with assault rifles - however, they had no ammunition, Mr Reist said.

Officials in Liechtenstein, which is on Switzerland's eastern borders, also sought to play down the incident.

Markus Amman, an interior ministry spokesman, said nobody in Liechtenstein had even noticed the soldiers. "It's not like they stormed over here with attack helicopters or something," he said.

If the Swiss had decided to invade and annex Liechtenstein, which has a population of around 34,000, it probably would have been a walkover. Liechtenstein is a quarter the size of the Isle of Man, and does not have an army.

The Swiss / Liechtenstein episode may stir memories for some of an accidental invasion of Spain by British marines five years ago after they misplaced Gibraltar while on exercises, much to the alarm of local fishermen.