Nearly 340,000 such migrants were seen so far this year arriving in the EU, mainly in Italy, Greece and Hungary. That was a 175 percent rise on the same period last year and much more than the 280,000 registered arrivals in all of 2014.
Other EU data shows 625,920 people claimed asylum in the bloc last year. Frontex officials were not immediately available to comment on how far the increase in numbers being detected may be a result of increased monitoring of the frontiers.
In Germany alone, which recorded 203,000 claims last year, officials expect to register some 750,000 refugees this year.
"Syrians and Afghans accounted for a lion’s share of the record number of migrants entering the EU illegally," Frontex said in a statement. "Most of them, fleeing instability in their home countries, initially entered Greece from Turkey."
Frontex Executive Director Fabrice Leggeri said: "This is an emergency situation for Europe that requires all EU member states to step in to support the national authorities who are taking on a massive number of migrants at its borders."
Italy detected more than 20,000 migrants last month, bringing the total number to 90,000 so far in 2015, most coming by sea from Libya. Some 90 percent of those are Africans, mainly from Eritrea and Nigeria.
Hungary reported detecting more than 34,800 people in July crossing its borders from non-EU states, notably via Serbia. Hungary will soon send thousands of policemen to its southern border to help secure it, a top government official said on Tuesday.