"The police intervention took place at Terminal 1 of the Airport [Humberto Delgado, in Lisbon], when citizens were trying to leave the Schengen area, likely destined for Ireland, using falsified passports, supposedly issued by authorities in Hong Kong and China," the PSP said in a statement.

The Schengen area is a free movement zone that includes 29 European countries, including Portugal, but not Ireland.

The six adults were detained on suspicion of committing the crime of falsifying or counterfeiting documents, while the seventh citizen, being under 16 years old, was identified, "and the legally prescribed procedures for the situation were adopted."

"The investigations carried out also made it possible to identify a common 'modus operandi' [method of operation], associated with the use of false documentation to try to circumvent border control mechanisms and circulate irregularly between European countries," the PSP emphasised.