A Greek MEP at the center of a graft scandal rocking the European Parliament and linked to Qatar protested her innocence in a Belgian court on Thursday and asked to be released from detention, AFP reported.

Eva Kaili, 44, was "cooperating in an active manner" with the Belgian federal prosecutor's investigation and was requesting to be released under electronic surveillance, her lawyer, Andre Risopoulos, said outside the Brussels courtroom.

Kaili had her powers as a vice president of the European Parliament suspended earlier this month over the corruption probe.

The decision came one day after she was arrested over suspected bribery by a Gulf state, believed to be Qatar, though Qatari officials have denied this.

Kaili was arrested on December 9 as Belgian police, searching a number of addresses, found 1.5 million euros in cash. Kaili was charged shortly afterwards, and has been in detention since.

Another three suspects were also arrested and charged with "criminal organization, corruption and money laundering", according to AFP.

A Belgian judge authorized Kaili's arrest and detention on grounds she was allegedly caught red-handed with cash, meaning her usual parliamentary immunity could not be invoked.

The MEP denies receiving money from Qatar in exchange for influencing decisions affecting it in the EU parliament.