Police have arrested a childless couple in Greece on suspicion of buying a baby Roma girl and trying to register her as their own.

The couple were arrested in Athens after they allegedly paid a Roma woman €4,000 for the baby, a Greek police statement said. Authorities are looking for the baby's birth parents.

The suspects, aged 53 and 48, were expected to be charged with child abduction. Under Greek law this includes cases where a minor is voluntarily given away by its parents outside the legal adoption process.

The arrests come amid international concern over another little girl who was found living with a Roma community in Greece.

Bulgarian authorities are trying to establish whether a local Roma woman is the mother of that child, a blonde-haired girl, aged about five, known as Maria.

The woman has been tested for a DNA match and served with preliminary charges of child selling, but has not been detained.

The case of Maria has drawn global attention, playing on the shocking possibility of children being stolen from their parents or sold by them.

But its handling by media and authorities has raised concerns of racism toward the European Union's estimated six million Gypsies.

Charges have been brought against the couple with whom Maria was found living in a Roma settlement outside Farsala, in central Greece, a week ago. They are being held in custody pending trial, and are also suspected of fraudulently obtaining birth certificates for a total 14 children.

The couple insist they were looking after Maria with their own five children after an informally-arranged adoption. The girl was placed into the care of a children's charity and her DNA details were provided to Interpol.

The police agency has so far failed to match her to any missing children declared in its records, from Poland to the US.

Separate inquiries are underway here after two children were removed from their parents by authorities - and subsequently returned - earlier this week.

On Wednesday, another Roma couple was charged with child abduction on the eastern Greek island of Lesvos. Police found them with a baby boy that was not their own.

The couple allegedly told authorities that they were childless and had been given the baby by a Roma woman in Athens who had five children.