Closer cooperation between Greek and Turkish coast guard authorities has led to 11,000 undocumented migrants being prevented from entering Greek borders and returned to the neighboring country since the start of the year, data presented by the Merchant Marine Ministry Friday showed.

Strife in the Middle East and Syria in particular has put increased pressure on patrols in the northern Aegean, with the ministry estimating that while 11,000 undocumented migrants were prevented from entering, as many as 30,000 or more have made it into Greece in the past 10 months alone.

The data presented Friday showed that from the start of the year until Thursday, a total of 29,281 undocumented migrants and 210 suspected traffickers were arrested during 1,063 interceptions.

“We are opposed to the concept of open borders, which is why we have elevated the issue of illegal migration to the top of the European agenda,” Merchant Marine Minister Miltiadis Varvitsiotis told Kathimerini Friday.

The ministry has also responded to the increased inflow of refugees and migrants in the Aegean by taking some 700 coast guard officers off their desk jobs, bringing the total number of officers conducting patrols to 2,500.

A report published last month by the European border agency Frontex showed a 50 percent hike in illegal migration to Greece and Spain in April-June compared with the same period last year.

Arrests at all European Union borders grew by 170 percent in the same period year-on-year, Frontex said.