IOM said the latest surge of people arriving in Greece was the highest weekly total so far this year, bringing the number of Mediterranean migrant arrivals in Europe to 681,000.
Amin Awad, the Middle East director for the UN refugee agency UNHCR, said Russian airstrikes and increased fighting around the Syrian city of Aleppo had contributed to the "dynamic of displacement", with about 30,000 displaced, but had not contributed much to the refugee exodus.
The UN Office for Co-ordination of Humanitarian Affairs puts the number at 50,000.
But Awad said the number of internally displaced people within Syria had fallen from 7.6 million people to 6.3 million, a decline that could be attributed to the refugee flows to Europe, as well as people being missed from the latest count.