The European Commission said in a statement on Thursday that it has sent formal letters to Greece, Italy and Croatia for the countries' failure to adequately register refugees entering the country.

"The European Commission sent administrative letters to Greece, Croatia and Italy in October. Two months later, concerns have not been effectively addressed. The European Commission has therefore decided today to send Letters of Formal Notice," the executive body said in a statement.

The submission of letters by the EU marks the first formal step in infringement proceedings.

The commission said that less than half of the tens of thousands of migrants that arrived in Greece were fingerprinted.

According to EU rules, refugees wishing to claim asylum must be registered in the first member state they step foot in.

However, the mass influx of migrants from war-torn countries in the Middle East, Asia and Africa has placed immense pressure on authorities in frontline countries, such as Greece and Italy.

Surge in arrivals

Eurostat, the EU's official statistics agency, reported on Thursday that more than 800,000 people applied for asylum in the 28-nation bloc during the first nine months of 2015.

"During the third quarter of 2015 (from July to September 2015), 413,000 first time asylum seekers applied for international protection in the Member States of the European Union, a number almost double that of the second quarter of 2015," Eurostat said in a statement.

Syrians comprised the largest group in the third quarter with more than 135,000 applications while Afghans and Iraqis made up the second and third largest group with 56,500 and 44,500 respectively.

In 2014, 626,065 people applied for asylum in the EU. This year is likely to see more than a million.

ls/jil (AP, Reuters, dpa)