Four members of the Islamist militant group Hamas have been detained on suspicion of planning attacks on Jewish institutions in Europe, German prosecutors said in a statement on Thursday.

Three of the suspects were detained in Berlin and another was detained in the Netherlands, according to the prosecutors.

Dutch national Nazih R was arrested by police in Rotterdam, while Lebanon-born Abdelhamid Al A and Ibrahim El-R, as well as Egyptian national Mohamed B, were arrested in the German capital, they said.

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.

European authorities have warned of an increased risk of attacks by Islamists radicalised by the Israel-Hamas war.