The latest estimate comes amid an intense discussion on migration within the EU, fuelled by public perceptions that the influx has risen dramatically.

The Geneva-based IOM noted that the 2015 figure was only slightly higher than in the comparable period last year.

The flow of people crossing the Mediterranean Sea traditionally increases in the summer months, when improved weather conditions encourage human smuggling to Italy or Greece.

"The rescue operations carried out by the international flotilla is a prelude to what is expected to be a surge of migrant crossings in the months ahead," IOM spokesperson Joel Millman said.

According to the IOM, more than 1 800 people lost their lives trying to reach Europe this year after fleeing conflicts or poverty, while 7 000 had been rescued.

Many of those who make the dangerous crossing are refugees, according to the UN refugee agency UNHCR.

The biggest groups come from conflict-torn Syria, the totalitarian east African country of Eritrea and Afghanistan.

However, a large percentage of the 102 000 did not recently flee conflicts or poverty, but had been waiting in countries along their journey to complete the trip to Europe, Millman said.

"A lot of people had been stuck," especially Syrians in Turkey, he said.

This was one of the reasons why Greece has seen a recent upsurge in people arriving on its islands, according to Millman. Some 46 200 migrants have arrived this year in Greece, compared with 34 000 for the whole of 2014.

UNHCR said authorities on Greek islands needed help quickly to take care of these people.

"UNHCR is calling for urgent reinforcement of personnel and resources of all the state services and civil society organisations dealing with the reception of refugees," the agency said in Geneva.

The IOM data showed that more than half of the year's arrivals - nearly 54 700 - have disembarked in Italy.