German authorities announced in a statement on Thursday that four members of the Islamist militant group Hamas had been arrested on suspicion of organizing attacks on Jewish institutions throughout Europe.

Prosecutors said that three of the suspects were being held in Berlin, while one was being held in the Netherlands.

Police added that Egyptian national Mohamed B, as well as Lebanese-born Abdelhamid Al A and Ibrahim El-R, were arrested in the German capital, while Dutch national Nazih R was detained in Rotterdam.

All four have been longstanding members of Hamas with close links to the leadership of the group’s military branch, said prosecutors.

Abdelhamid Al A had been tasked by Hamas leaders in Lebanon with sourcing weapons. The weapons were due to be taken to Berlin and kept at the ready for potential terrorist attacks against Jewish institutions, said prosecutors.

“Following the terrible attacks by Hamas on the Israeli population, attacks on Jews in Jewish institutions have also increased in our country in recent weeks,” said German Justice Minister Marco Buschmann in a statement on the detentions.

“We must therefore do everything we can to ensure that Jews in our country do not have to fear for their safety again,” he said.