Police in Finland are calling on the public to check their passports to see whether they have defective watermarks, as this could cause problems when travelling.

The National Police Board also warned border guards to be on the look-out for the flaws, namely upside-down watermarks and mismatched page numbers, Finland's Yle national broadcaster reports.

It turns out that watermarks were printed upside-down in two series of passports. Between 2012 and 2016 the swan watermark was printed the wrong way round, and in passports issued since 2017 the problem watermark is a bear.

In addition, there are cases where the watermark impressions of page numbers do not match the actual pages.

'Very annoying'
Although the company that prints the passports changed in 2016, the manufacturing fault has reoccurred, which Police Board Senior Advisor Mika Hansson told Yle is "very annoying".

The watermark problem does not invalidate the passports, but can cause problems abroad. The police were alerted to the problem last month, when Russian border guards denied entry to five Finnish travellers because of defective passports.

Finnish passports are decorated with the country's wildlife, and one source of national pride is that flipping through the pages makes the image of an elk canter by.

If anyone finds a problem with their passports they should return them to the police, who will replace them free of charge. Mika Hansson was not able to give the precise number of passports that have already been handed in, but said it was a matter of "individual cases".

And anyone hoping that they will get a fresh 10-year passport will be disappointed - the replacement will have the same expiry date as the original.