By Ozgun Tiran

KIRKLARELI, Turkey

At least 33 irregular migrants were held in northwestern Turkey, security sources said on Saturday.  

The local gendarmerie forces launched an operation upon a tip-off, catching five separate groups in Kirklareli province, near the border with Bulgaria, said the sources, who asked not to be named due to restrictions on speaking to the media.  

The migrants -- Afghan, Iraqi, Iranian and Pakistani nationals -- were allegedly preparing to illegally cross to Europe, the sources said.

They were later referred to provincial migration directorate.

In recent years, Turkey has been a main route for irregular migrants trying to cross to Europe, especially since 2011, the start of the Syrian civil war.  

Over 265,000 irregular migrants were held in Turkey last year, according to the Interior Ministry.