Police in the Netherlands and Germany have arrested two men for allegedly recruiting jihadi fighters to go to Iraq and Syria, Dutch police said Thursday.

A woman was also held with the man arrested in Germany as part of a long-running investigation, police said in a statement.

All three are from The Hague and are accused of inciting hatred through social media and plotting terror attacks, police said, likely referring to help allegedly given to would-be Islamist fighters to reach the Middle East.

"The two male suspects are suspected of recruiting for the armed terrorist struggle in Syria and/or Iraq and conspiring to commit murder with terrorist intent," the statement said.

Dutch police said they raided four homes as part of the operation.

State broadcaster NOS said that the man, 32, and woman, 24, arrested in Germany were a married couple.

The man was allegedly involved in demonstrations in Dutch capital in July during which some protesters shouted "Death to the Jews" in Arabic and waved black jihad flags, NOS said, citing unnamed sources.

Nine people have so far been arrested as part of an investigation into would-be Dutch jihadis which began in April 2013, police said, with five still in custody.

More arrests could follow, police said.

The growing numbers of Westerners joining the Islamic State (IS) and other extremist groups has raised fears that they could return home and carry out attacks.

An estimated 130 Dutch citizens have gone to fight in Syria and Iraq, Dutch authorities say. Around 30 have returned while 14 were killed in the fighting, according to the Dutch intelligence service AIVD.

Dutch jihadis have carried out at least one suicide attack in Syria and one in Iraq, according to the Dutch NCTV counter-terrorism agency.

Several people have been arrested allegedly on their way to fight jihad, while others have had their passports confiscated to prevent them travelling.

Dutch counter-terrorism chief Dick Schoof said in June that recent military successes by IS would encourage a new wave of European Muslims to go and fight in the Middle East.