Greece served as the gateway to the European Union for more than one million Syrian refugees and other migrants in recent years. While an agreement with Turkey sharply reduced the number attempting the voyage since 2016, Greek islands still struggle with overcrowded camps operating far beyond their capacity.

The 2.7 kilometre long (1.68 miles) net-like barrier that Greece wants to buy will be set up in the sea off the island of Lesbos, where the overcrowded Moria camp operates.

It will rise 50 centimeters above sea level and carry light marks that will make it visible at night, a government document inviting vendors to submit offers said, adding that it was “aimed at containing the increasing inflows of migrants”.

“The invitation for floating barriers is in the right direction,” Defence Minister Nikos Panagiotopoulos told Skai Radio. “We will see what the result, what its effect as a deterrent will be in practice.”

“It will be a natural barrier. If it works like the one in Evros… it can be effective,” he said, referring to a cement and barbed-wire fence Greece set up in 2012 along its northern border with Turkey to stop a rise in migrants crossing there.

Aid groups, which have described the living conditions at migrant camps as appalling, said fences in Europe had not deterred arrivals and that Greece should focus on speeding up the processing of asylum requests instead.

“We see, in recent years, a surge in the number of barriers that are being erected but yet people continue to flee,” Βoris Cheshirkov, spokesman in Greece for U.N. refugee agency UNHCR, told Reuters. “Greece has to have fast procedures to ensure that people have access to asylum quickly when they need it.”

Last year, 59,726 migrants and refugees reached Greece’s shores according to the UN agency UNHCR. Nearly 80% of them arrived on Chios, Samos and Lesbos.

A defence ministry official told Reuters the floating fence would be installed at the north of Lesbos, where migrants attempt to cross over due to the short distance from Turkey.

If the 500,000 euro barrier is effective, more parts may be added and it could reach up to 15 kilometres, the official said. (Reporting by Renee Maltezou, Lefteris Papadimas and Angeliki Koutantou Editing by Peter Graff and Gareth Jones)