The International Organization for Migration says refugee and migrant arrivals by sea and land into Europe this year are expected to top the 1 million mark next week.

The Geneva-based agency says 990,761 people have arrived from Africa or the Middle East, with more than 800,000 people crossing from Turkey to Greece alone. More than half of those — or some 455,000 — are Syrians.

IOM spokesman Joel Millman said roughly 4,300 people arrived from the Turkish coast to nearby Greek islands on Wednesday. The agency now estimates the one-million mark will be reached by Tuesday. That would be over four times the total of about 240,000 crossings by land and sea into Europe last year.

The agency said daily arrivals continue in the thousands despite "ever colder temperatures and dangerous sea conditions."