The ABW said examples of unusual activity could include watching a bridge or train station for an extended period, photographing infrastructure or asking unusual questions.
Other examples include a camera appearing in a place where there was previously none or a drone flying near a strategic site.
Such situations do not necessarily indicate a threat, but they could be part of a larger pattern, the ABW said.
The agency urged people not to share photos or locations of such activity online.
Anyone who observes unusual activity should report it to the ABW by calling (+48) 22 585 82 21 or through the agency's Telegram chatbot: bot@ABW_STOPdywersji_bot.
(sp/gs)
Source: IAR/PAP