Greek authorities have arrested four policemen for trafficking hundreds of Eastern European women for prostitution, the police said.

"It is Greece's biggest trafficking case in the last 15 years," a police official said, adding that a retired police officer, who recruited the women, was also arrested.

"All five were the masterminds of the ring," said the official, who requested anonymity.

The ring was responsible for bringing about 300 women to several night clubs in Athens over the past few months, he said.

In a separate case, Greece arrested another policeman for human trafficking and drug dealing on Wednesday, the official said.

International pressure is rising on Greece to fight trafficking. A U.S. government report released last month said Greece needs to do more to punish offenders, whom it said often include government officials and policemen.

Despite 21 convictions last year, many offenders are released pending lengthy appeals and courts often give them suspended sentences, the report said.

Greece is a destination and transit country for trafficking of women and children from countries including Eastern Europe and Nigeria.