BERLIN — Germany’s top court has blocked the extradition to the United States of a Turkish man accused of stealing almost $60 million in a series of hacking raids against credit card companies.

Ercan Findikoglu was arrested at Frankfurt Airport in December 2013. U.S. authorities accuse him of masterminding a group that carried out the online heists between 2011 and 2013.

The group allegedly hacked into the computer networks of payment processing companies to raise the limits on prepaid credit cards and withdraw large sums of money.

The Federal Constitutional Court said Tuesday that judges granted Findikoglu’s appeal against a lower court decision to permit his extradition.

It said Frankfurt’s regional court needs to obtain assurances from U.S. authorities that the defendant won’t face a disproportionate sentence if convicted.