The Greek police force says its crackdown on illegal immigration, which has led to almost 6,700 people being detained and just over 1,500 arrested since last Saturday, is already producing results.

Authorities said the number of migrants entering Greece via the country’s Evros border with Turkey has fallen dramatically. According to figures released by the police, 447 undocumented migrants were caught crossing into Greece illegally on August 2, before the Xenios Zeus operation began, but on Wednesday and Thursday this week that figure had fallen to 12 and 15 respectively.

The police presence on the border was also strengthened last week, with more than 1,800 border guards being transferred to the Evros region.

“The reduction has been achieved before we deployed the full means at our disposal to tackle illegal immigration,” the police said in statement.

The number of patrol boats on the Evros River is due to rise to 26 over the next few days. Also, 50 specially trained dogs are due to join border patrols. Border guards are also expected to be given thermal cameras to detect migrants and traffickers at night.

“As the days go by, the flow of illegal immigrants into Greece will become smaller,” Babis Pantelidis, the head of the Evros border guards’ union told Kathimerini.

According to Panayiotis Harelas, who heads the federation of border guards, 1,600 of the 1,881 border guards transferred to the area just over a week ago have joined patrols. The remainder are on duty in Xanthi and Rhodope.

“We estimate that on each shift, there are between 300 and 400 patrolling the length of the border,” said Harelas.

The police said that the crackdown on illegal immigrants in Attica has also led to the arrest of more than 50 sex workers, 10 of whom were found to be HIV positive. Raids on two warehouses have also led to 2.5 million counterfeit items intended for sale being seized.

Human rights groups have called on Greece to stop the Xenios Zeus operation, arguing that its stop-and-search policy is discriminatory and that it will fuel further attacks on migrants.