A migrant woman hugs her children, moments after arriving on a dinghy on the Greek island of Kos, August 18, 2015. [Photo/Agencies]

BRUSSELS - More than three times as many migrants were tracked entering the European Union by irregular means last month than a year ago, official data showed on Tuesday, many of them landing on Greek islands after fleeing conflict in Syria.

While the increase recorded by the European Union's border control agency Frontex may be partly due to better monitoring, it highlighted the scale of a crisis that has led to more than 2,000 deaths this year as desperate migrants take to rickety boats.

Italian police said they had arrested eight suspected human traffickers that they said had reportedly forced migrants to stay in the hold of a fishing boat in the Mediterranean as 49 of them suffocated on engine fumes.

Some of those traffickers were accused of kicking the heads of the migrants when they tried to climb out of the hold as the air became unbreathable, prosecutor Michelangelo Patane told a news conference in Catania, Sicily.

The dead migrants were discovered last weekend, packed into a fishing boat also carrying 312 others trying to cross the Mediterranean to Italy from North Africa.

It was the third mass fatality in the Mediterranean this month: last week, up to 50 migrants were unaccounted for when their rubber dinghy sank, a few days after some 200 were presumed dead when their boat capsized off Libya.

Greece appealed to its European Union partners to come up with a comprehensive strategy to deal with what new data showed were 21,000 refugees landed on Greek shores last week alone.

A spokesman for the United Nations refugee agency UNHCR in Geneva said the European Union should help Greece but that Athens, which is struggling with a debt crisis, also needed to show 'much more leadership' on the issue.

Greek officials said they needed better coordination within the European Union. "This problem cannot be solved by imposing stringent legal processes in Greece, and, certainly, not by overturning the boats," said government spokeswoman Olga Gerovassili.

Nor could it be addressed by building fences, she said.