ATHENS -- Human rights group Amnesty International on Friday called on Greece to investigate the case of 13 Afghan immigrants, including eight minors, who accuse members of the Greek coastguard of mistreating and robbing them.

In statements to Amnesty in January, the migrants said they were intercepted by the crews of two vessels flying the Greek flag off the island of Lesvos.

The uniformed men, some of whom were wearing hoods, allegedly beat several of the migrants -- including two boys aged 9 and 13.

They also allegedly tore through the migrants' baggage with knives, stripped some of them down to their underwear and took their cellphones and money.

They subsequently put them in inflatable dinghies, punctured them, and told them to return to Turkey, according to the testimony given by the migrants, who are in Turkish detention at the coastal town of Ayvalik, Amnesty said.

"Such an act could endanger the migrants' lives and is a clear violation of Greece's responsibilities under its international and European obligations," Amnesty said.

Amnesty noted that the migrants' story is consistent with other reports of rights violations it has received in recent months.

Human rights groups regularly castigate Greek authorities for their treatment of illegal immigrants and for failing to provide asylum-seekers with information on their rights to sanctuary.

In October, the German-based PRO ASYL group released a report detailing cases where coastguards beat migrants to extract information on smuggling operations.

The group also said the Greek coastguard routinely tries to block migrants' boats and force them out of Greek territorial waters.

Greece said it would investigate these cases, and officials stress that Greek border guards are hard-pressed to deal with the thousands of migrants who try to penetrate the EU's southeastern border every year.

But Amnesty noted that it has yet to receive information from the Greek merchant marine ministry on the coastguards' training and chain of command in response to a request filed nearly two months ago.

Internal coastguard probes rarely result in charges being filed.