At least eight Pakistani refugees on their way from Turkey to Greece were reported missing on Monday after their boat capsized off the Kos island, the media reported.
As many as five people, who managed to swim to the shore and alerted the authorities, said all those missing were Pakistani, Xinhua reported.
A rescue operation was under way though high speed winds prevailed in the area.
Monday's tragedy occurred as more than 44,000 refugees and migrants remain stranded in Greece after the gradual closing of borders along the Balkan route to central Europe since mid-February.
According to the latest figures from the Migration Policy Ministry, approximately 12,000 people remain at the overcrowded muddy makeshift camp of Idomeni near the crossing at the Greece-Macedonia border, living in horrible conditions with inadequate food and medicine.
About 9,000 people are still on the Aegean Sea islands, another 11,000 across the Greek capital and its suburbs, more than 3,000 in the passenger terminals of Piraeus port and 1,000 scattered at hospitality centres in central Greece.
Since only a few dozen Syrians and Iraqis are allowed to enter Macedonia each day, desperate refugees keep crossing the Aegean, risking their lives to reach Greek soil.
According to the Greek Shipping Ministry, about 2,000 people continue to reach the Greek islands per day on boats from Turkey despite the latest agreement between the EU and Turkey for closer cooperation to prevent the refugee influx.
