A riot police officer patrols outside Koridallos prison in Athens May 3, 2015. According to Greek Police, two inmates of Pakistani nationality died, and 21 were injured during a brawl among inmates on Sunday. [Photo/Agencies]

ATHENS - Two inmates lost their lives and twenty one were injured - among them six seriously - during clashes between prisoners inside Greece's maximum security prison at the Piraeus port suburb of Korydallos, Greek police said on Sunday.

The two dead were Pakistani nationals according to initial information by police sources.

The violent scuffles between mainly Albanian, Arab and Pakistani prisoners with makeshift knives and other objects lasted for about half an hour, according to reports.

The incident happened at a prison section where about 500 convicts for drug - related cases were held.