What began as a routine training exercise for some Swiss soldiers almost ended in an embarrassing diplomatic incident when the troops got lost at night and mistakenly marched into neighbouring Liechtenstein.

According to the Swiss newspaper Blick, the 170 infantry soldiers from the neutral country wandered more than 1.5 kilometres across an unmarked border into the tiny principality early Thursday, but they soon realized their mistake and turned back.

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

Officials in Liechtenstein also played down the incident, with Interior Ministry spokesman Markus Amman saying nobody in his country had even noticed the soldiers, who were carrying assault rifles but no ammunition.

"It's not like they stormed over here with attack helicopters or something," he said.

Liechtenstein, which has 34,000 citizens but no army, covers 160 square kilometres, about a quarter of the size of Toronto.