European police have amped security forces after receiving warning from a “friendly” intelligence service that capital cities across the continent could be targets of a terrorist attack before the end of December.

Viennese police confirmed that an unnamed intelligence service had warned Austria days before Christmas that there would be a possible shooting or bomb attack between Christmas and New Year’s Eve.

Officials have tightened surveillance, ID checks and alertness for objects that could be carrying explosive devices.

A German government spokesman said that increased measures had been adopted following the attacks in Paris on November 13.