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The number of migrants and refugees crossing the Aegean Sea from Turkey to Greece has increased by 500 percent since last year, according to European border control agency Frontex. In comparison, the number of migrants attempting the perilous journey across of the Mediterranean to Italy has gone up just 5 percent, Frontex executive director Fabrice Leggeri said Wednesday.

"When you close off a migration route, another one opens up elsewhere," Thibaut Jaulin, a research fellow at the Center for International Studies and Research (CERI) at Sciences Po in Paris, told VICE News.

European authorities have beefed up surveillance along the Libya-Italy migrant route in an effort to prevent the recurring tragedies in the Mediterranean. In April, naval border monitoring operation Triton saw its budget tripled from 3 million euros ($3.4 million) to 9 million euros ($10.2 million) a month.

The European Council is also considering launching a military operation in Libyan waters to destroy boats used by Libyan people smugglers. The EU is due to vote on the issue on June 22. The move will also need to be approved by Libya or by the UN Security Council.

According to Frontex, the "Eastern Mediterranean Route" — described as "the passage used by migrants crossing through Turkey to the European Union via Greece, southern Bulgaria or Cyprus" — is not a new path for migrants. Since 2008, the route has become the second biggest "migratory hot spot" in the EU, and it was Europe's "second largest area for detections of illegal border-crossings" in 2014.

Leggeri told French daily Les Échos on Wednesday that some 37,000 migrants had arrived on Europe's shores through Italy since the beginning of 2015, versus 40,000 through Greece.

According to Jaulin, authorities have increased monitoring along the land route between Turkey and Europe, which passes either through southern Bulgaria or eastern Greece. To avoid the border patrols, the researcher explained, migrants attempt the dangerous crossing to Greece aboard inflatable dinghies. "Once they arrive on [one of the islands], their plan is to reach the mainland by ferry," he said.

In early 2015, VICE News traveled to the border between Greece and Turkey, where Syrian and Afghan refugees are paying large sums of money to take "death boats" to Greece.

Leggeri also highlighted the plight of migrants fleeing the conflict in Syria. According to the head of Frontex, "almost 100 percent" of all migrants from the country receive refugee status in the EU. Close to 4 million Syrians have fled their homeland, according to UNHCR, and they are now the largest refugee population in the world.

Leggeri said that the number of Syrian refugees in Italy was on a downward trend, which could explain the surge in migrants traveling along the Eastern Mediterranean route. "Syrian families would rather avoid Libya, because the security conditions there have gotten worse," Leggeri told Les Echos. "The smugglers are much more brutal in Libya."

A few months ago, VICE News traveled to detention centers in Libya, where migrants spoke of torture and serious human rights violations.

Leggeri also said that Frontex had recorded 100,000 illegal border crossings since the start of 2015, 60,000 more than were recorded during the same period last year. He attributed the surge to a wave of illegal migration into the EU from Kosovo between January and March.