German authorities say they have made four arrests of suspected Hamas members linked to an alleged plot to attack Jewish sites.
Prosecutors said the suspects intended to store weapons in Berlin for possible use in an attack.
Danish authorities also said they had arrested three people accused of preparing an attack.
Denmark’s intelligence agency said the Danish and German investigations were not directly linked.
German prosecutors said in a statement that three suspects linked to Hamas were arrested in Berlin and one in the Netherlands. Hamas, which runs Gaza, is banned across Europe as a terrorist group.
The arrests came after police raided five apartments and a restaurant in Berlin, German media reported.
The three held in Berlin were Lebanese and Egyptian, according to German prosecutors.
The fourth suspect, a Dutch national, was picked up in Rotterdam by Dutch police who were acting on information from the German authorities.
All four are believed to be long-standing members of Hamas.
The German prosecutors said the four were “closely linked” to the leadership of Hamas’s armed wing, the Ezzedine al-Qassam Brigades.
They added that one of the four, named as Abdelhamid Al A, had been tasked by Hamas leaders in Lebanon with locating a “depot with weapons in Europe, which the organisation had covertly set up there in the past”.
“The weapons were due to be taken to Berlin and kept in a state of readiness in view of potential terrorist attacks against Jewish institutions in Europe.”
Ch Insp Flemming Drejer of the Danish police said the three suspects arrested in Denmark as part of its own investigation would be charged with terror offences.
Danish Prime Minister Mette Frederiksen said the threat was “as serious as it gets”.
Later, Denmark’s PET security and intelligence agency clarified that there was “no direct connection” between the arrests in Denmark and those in Germany.
The office of Israeli Prime Minister Benjamin Netanyahu wrote in a statement on X (formerly Twitter) that the seven people arrested were “acting on behalf of Hamas”. But while federal prosecutors in Germany have linked the plot to Hamas, Danish authorities have not said the group is connected to their own investigation.
Danish Justice Minister Peter Hummelgaard said the alleged plot “tragically confirms that Danish Jews are under threat”.
Those arrested in Denmark were scheduled to appear in closed court hearings on Thursday.
Ch Insp Drejer said an investigation had uncovered a transnational network of people preparing an attack, with links to criminal gangs.
Security around Jewish sites would be reinforced and police patrols in Copenhagen made more frequent, he added.
Danish intelligence chief Anja Dalgaard-Nielsen said the terror threat was linked to the Israel-Gaza war and burnings of the Quran in Denmark and neighbouring Sweden.
Earlier this month, EU Home Affairs Commissioner Ylva Johansson warned that Europe faced a “huge risk” of terrorist attacks over the Christmas period.
In 2015, two people were killed in an attack on a cultural centre and a synagogue in Copenhagen.
The terror threat in Denmark currently stands at level four out of five, the second-highest. The PET security and intelligence agency says the main threat to Denmark comes from militant Islamists, most likely from” a small group or a lone actor” inspired by propaganda.
Mr Hummelgaard said the government currently saw no reason to raise the threat level.