Thanassis Stavrakis, Associated Press
A girl looks at Syrians refugees during a protest over a lack of translator and the slow asylum process outside the Central Asylum Center in Athens, Thursday, May 14, 2015. This year has seen a significant increase in the numbers of refugees from war-torn Middle Eastern and African countries, as well as economic migrants, crossing illegally to Greece.

BRUSSELS — The European Union's border agency is boosting its operations in the Mediterranean near Greece as increasing numbers of migrants try to enter the EU from Turkey, its head said Thursday.

Frontex Executive Director Fabrice Leggeri told The Associated Press: "We are worried about the situation in Greece and that's why we will upgrade our action there and our support to the Greek authorities."

More than 10,000 people have been plucked from the central Mediterranean in recent weeks attempting to enter Europe from Libya in overcrowded and unseaworthy boats. Some 1,700 are feared dead.

"There is a shift from the central Mediterranean to the eastern Mediterranean" as more migrants leave Turkey by sea and land, Leggeri said.

"They are moving very quickly so we have to be flexible."

Earlier Thursday, police in northern Greece said that 93 Syrian migrants were released from a locked cargo train carriage, after being tricked by smugglers into traveling in the wrong direction.

The number of Syrians reaching Greece has surged in the past year as the civil war in their country continues into a fifth year.

Many make the short hop from Turkey's southwest coast toward the island of Lesbos some 9 kilometers (5 miles) away in inflatable rafts. From there they often try to board ferries and move further north into Europe.

But others choose to travel by land through western Turkey and across the Greek and Bulgarian borders, where the Frontex presence is also being stepped up.