The PET rated the overall threat level at 4 out of 5, but said the risks within that level had increased.

“The conflict between Israel and a number of rebel groups is of course of concern to many people, including in Denmark,” PET said in a statement.

“The conflict also contains a significant potential for radicalisation and mobilisation, which can potentially activate actors for spontaneous or planned reactions in Denmark, including terrorist attacks.”

Anti-Islam activists last year damaged several copies of the Quran in Denmark and also in neighbouring Sweden, two of the most liberal countries in the world, which have allowed trenchant criticism of religion in the name of free speech.

Sweden raised its terrorism alert to the second highest level, saying it had thwarted attacks after the Quran burnings and other acts against Islam’s holiest text that triggered threats from jihadists.

Denmark’s parliament in December passed a law making it illegal to burn the Quran in public places, seeking to defuse tensions with Muslim countries.