GETTY Serbia has secret plans to build a border fence if a fresh influx of migrants occurs

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States in central Europe and the Balkans have been put on red alert for another massive wave of asylum seekers after Recep Tayyip Erdogan handed the extraordinary blackmail note to EU leaders. And now Serbia has revealed it has drawn up emergency plans to follow in the footsteps of neighbours Bulgaria, Macedonia and Croatia in constructing a huge barrier which would seal off most of the continent.

The extraordinary measure was leaked by Government insiders who said ministers fear Islamist despot Erdogan is about to unleash a “tsunami” of three millions migrants on Europe. They told the state-owned Novosti newspaper that the already prepared “Plan B” could be enacted within a short timeframe to protect the country from any further refugee chaos.

GETTY Neighbouring countries including Hungary have already put up walls at their frontiers

GETTY The numbers using the Balkans route has dropped, but Turkey is threatening to scrap an EU deal

The paper reported: "If Turkey, as its leader Recep Tayyip Erdogan threatened yesterday, opens the border for refugees from Syria, Afghanistan, Iraq and other countries that are on its territory...the Serbian government has prepared a 'plan B'. "It will be activated and a proposal will be discussed for our country, just like our neighbours, to build a wall on its southern borders." Serbia - which is not an EU member - is a vital transit point on the migrant journey northwards from Greece towards the promised lands of Germany and Sweden. But as neighbouring countries including Hungary to the north have taken an increasingly tough stance on immigration, putting up their own border fences, more and more refugees have become trapped there.

We urge the Government to urgently take the decision to build a wall on the border with Macedonia to halt the uncontrolled influx of migrants into Serbia Opposition leader Nenad Popović

Government officials said there are around 5,200 asylum seekers registered in the tiny eastern European state, with a further 1,000 living on the streets - mostly in the capital Belgrade. And labour minister Aleksandar Vulin confirmed that the authorities have been planning for the potential collapse of the EU-Turkey migrant deal, saying border controls with its southern neighbour Bulgaria - which is in the EU - would be “significantly” beefed up. Nenad Popović, leader of the opposition Serbian People’s Party, also called for the construction of a wall after Novosti published a leader article headlined: “We are threatened with a ‘tsunami’ of 3,000,000 migrants!” He said: “We urge the Government to urgently take the decision to build a wall on the border with Macedonia to halt the uncontrolled influx of migrants into Serbia.”

Borders across the world Sat, March 19, 2016 See the structures that are intended to prevent migrants from crossing the borders across the globe. Play slideshow EPA 1 of 26 Hungarian Army patrol the area along the temporary border fence on the Hungarian-Serbian border