The United Nations refugee agency says some 224,000 migrants and refugees have crossed the Mediterranean to Europe so far this year.

William Spindler, a spokesman for the United Nations High Commissioner for Refugees (UNHCR), said that by the end of July, around 224,000 refugees had arrived in Europe by sea.

Spindler also warned that the continent could brace and grapple with a high-scale refugee crisis.

“What we have at Europe's doorstep is a refugee crisis,” Spindler told the AFP news agency in an email on Thursday.

About all of the refugees crossing the Mediterranean during that period, often in rickety boats and at the mercy of human traffickers, have landed in Greece and Italy, the UN official added.

In this handout picture taken on May 3, 2015 and released by the MOAS (Migrant Offshore Aid Station) migrants wait aboard a wooden boat during a rescue operation off the coast of Sicily in the Mediterranean. (© AFP)

Spindler also noted that more than 2,100 people have drowned or gone missing during perilous journey across the Mediterranean over the past seven months.

The remarks come as over 200 migrants attempting the perilous journey across the Mediterranean reportedly drowned on Wednesday after their overcrowded fishing boat capsized off Libya.

The boat is believed to have been carrying over 600 migrants, including several women and children. Sources say around 400 people had been rescued from the water while 25 bodies had been recovered.

The UNHCR earlier called on the European governments to provide legal alternatives so that desperate people in need of refuge can seek and find protection and asylum.