Greek authorities arrested five border police officers Tuesday on suspicions of working with a human smuggling network that illegally brought migrants into the country from Türkiye.

The five men appeared before a prosecutor in the northeastern city of Orestiada (Kumçiftliği), a day after the police department's internal affairs division said they had been arrested on suspicion of taking bribes and breach of duty.

They are accused of helping to smuggle an unknown number of migrants on at least 12 occasions in the Didymoteicho area in northeastern Greece, the police said in a statement.

"An investigation so far has shown that the officers had been in contact with networks operating in a neighboring country at least since October, and allegedly carried out actions or omissions aimed at facilitating the entry of (non-EU) nationals into our country," it said.

Evidence linked to the case includes nearly 60 cell phones and foreign currency from a number of countries, the police said.

Thousands of migrants, mainly from Syria, Afghanistan and Pakistan, have in recent years attempted to cross into Greece from Türkiye in the hope of making it to Western Europe.

With the stepping up of patrols in the Aegean Sea making it harder for migrants to reach Greek islands, more are taking their chances by crossing the River Evros, Greece's natural border with Türkiye, and having traffickers take them from there by road.

Athens has decided to extend by 35 kilometers (22 miles) a 5-meter high steel fence that runs along the river.

The fence is currently 38 kilometers long, and Athens aims to carry out the extension within a year, adding a total of 100 kilometers by 2026.

Greece, however, has also been accused of inhuman practices against illegal migrants. With the help of the European Union's border agency, Frontex, it has deliberately and systematically pushed back asylum-seekers toward Türkiye, according to an investigation by the European Anti-Fraud Office (OLAF).