Anis Amri murdered a Polish truck driver and shot an Italian policeman with a handgun freely available on the black market in Europe for just 150 euros.

The ISIS terrorist's 22 caliber pistol was photographed next to his body where he was shot dead after a shoot out in Milan at 3am today.

It raises questions about how Amri was able to secure the weapon despite being under surveillance by the German authorities and being arrested by police at least three times this year.

The 24-year-old was even recorded by the security services telling a hate preacher he was willing to be a suicide bomber two months ago.

Terrorists are finding it easier than ever to get guns because of the flow of illegal weapons flowing from the Balkans into the heart of western Europe.

Evidence: Tunisian Anis Amri pulled this gun from his backpack before being shot dead. It is the same weapon used to kill the Polish lorry driver who was hijacked in Berlin

Crime scene: Berlin truck terrorist Anis Amri has been shot dead after a gunfight with police in Milan in the early hours of this morning

Experts from the Switzerland-based Small Arms Survey estimate there are between 3million and 6million guns left over from wars during the 1990s. Up to 1.5million of them are said to be in Serbia - a legacy of the break-up of Yugoslavia.

A simple hand gun is no more than 150 euros and more expensive weapons like AK-47s will cost as little as 700 euros and are delivered to you by criminal gangs.

Speaking in 2015, an arms dealer known as 'the German' described how guns are being sold to terrorists all the time.

He said: 'There are plenty of nooks and crannies in a car or truck where you can hide a disassembled gun. People hide them in the fuel tank.

'Silenced weapons cost more, sub-machine guns that are easier to conceal, they cost more. Pistols are still fairly cheap, around 150 euros apiece.'

Ivan Zverzhanovski, who runs a UN project in Belgrade to reduce gun crime said: 'You don't know where these weapons are, who holds them or how they are being used.

'You don’t need hundreds of thousands of weapons. You just need enough to create havoc.

'The gun market operates on a very basic supply and demand system. Since about 2011, there has definitely been a significant increase of illicit weapons going from southeast Europe towards different parts of the EU'.

The Berlin attack suspect has been shot dead after a gunfight with police in Milan, Italian police have said

Revealed: Experts from the Switzerland-based Small Arms Survey estimate these are the number of guns in the Balkans

Anis Amri became Europe's most wanted man after murdering 12 people and injuring 48 more by driving a lorry through a packed Christmas market on Monday.

But he had been involved in crime from the age of 17, including drug dealing and violent robbery, and had links to gangs who would have access to guns.

More recently, after he was radicalised and pledged to die for ISIS, he met and spoke with known hate preachers and extremists with links to violent jihad.

These groups will also likely have access to guns, or have to money to buy them, especially ones smuggled back into Europe by the thousands of ISIS fighters who have returned from Syria.

Amri had offered to carry out suicide attacks for Islamic State, it emerged yesterday.

Journey: Amri fled Tunisia before posing as a child migrant, arriving on the small island of Lampedusa. He was jailed in Italy then entered Germany under a false identity

The 24-year-old was recorded by the security services making the offer to a hate preacher two months ago, sources revealed.

But in yet another blunder by the German authorities, which were monitoring his movements, he was left at large.

It also emerged that Amri was sentenced to five years in absentia in his home country of Tunisia for an armed robbery after he fled. And it was reported that he was given a jail term there in 2010 for stealing a HGV similar to the one used to murder 12 and injure 56 at the Christmas market in Berlin on Monday night.

He arrived in Italy in 2011, arriving on the small island of Lampedusa amongst thousands of people fleeing the Arab Spring uprisings. He pretended to be a child migrant - even though he was 19 - but then rioted inside his detention centre, which was set on fire. He was then jailed for four years, serving it in two prisons on Sicily.

After his release Italy failed to deport him twice because Tunisia refused to take him back and he fled Italy via the Alps for Germany, meaning he probably went via Milan.