German authorities say they have arrested three young men suspected of giving money to members of the Islamic State group and planning to fight for it.

Stuttgart prosecutors said the three — a 25-year-old German national and two Turkish citizens aged 20 and 25 — were arrested in and around the southern city of Ulm on Sunday on suspicion of financing terrorism.

Prosecutors said in a statement Wednesday that authorities had already banned the three from leaving Germany to prevent them heading off to train with IS. They said the men are suspected of sending money, collected while distributing copies of the Quran, directly or indirectly to members of IS.

A judge on Monday ordered the men, whose names weren't given, held in custody pending possible charges.