Mehdi Ben Nasr, the leader of an al-Qaeda-affiliated terrorist group was smuggled into Europe posing as a refugee trying to cross the Mediterranean

The leader of an al-Qaeda-affiliated terrorist group was smuggled into Europe posing as a refugee trying to cross the Mediterranean, it has been claimed.

Mehdi Ben Nasr, 38, served seven years in jail for being the leader of a jihadi cell which recruited would-be suicide bombers in Europe and directed them to Iraq and Afghanistan.

European leaders have denied that there is evidence of jihadis exploiting the refugee crisis by disguising themselves as migrants and joining them on crossings.

But intelligence analysts have warned that would-be militants could be using the migrant routes to reach Europe undetected.

Once ashore in countries such as Italy and Greece, it is feared that militants could side-step identification by the authorities – and plot violent attacks on European cities.

Mehdi was arrested in 2007 in a Europe wide anti-terrorism operation in 2007.

During the operation in Britain, France and Portugal as well as Italy police seized poisons, remote explosive detonators and Al Qaeda manuals on guerrilla warfare.

Mehdi was 'a terrorist of the most dangerous kind' because he was a explosives expert and the 'North Star' of the group that recruited and arranged the travel of would-be jihadis to the Middle east,' Italian intelligence sources told Il Giornale

He was deported to Tunisia last year after serving his sentence in Italy.

But in October he attempted to conceal himself among 200 refugees rescued by an Italian warship in the Mediterranean.

Mehdi arrived in Sicily on October 4 giving the fake name Mohamed Ben Sar and claiming political asylum.

He was arrested on suspicion of trafficking.

Police in Agrigento said: 'On 7 October 2015, four foreign citizens of Tunisian nationality were arrested accused of aiding illegal immigration.'

In October Medhi attempted to conceal himself among 200 refugees rescued by an Italian warship in the Mediterranean

Intelligence analysts have warned that would-be militants could be using the migrant routes to reach Europe undetected

'As a result of the investigation it emerged that the immigrants had already been expelled from Italy but reentered via Lampedusa along with migrants of various ethnicities.'

The Tunisian has been redeported and handed over to Tunisian police.

Mehdi was one of 14 Algerians and Tunisians arrested in 2007 including two in London. Ali Ben Zidane Chehidi and Mohamed Salah Ben Hamadi Khemiri, were arrested in the UK accused of forging documents for jihadis. They were extradited to Italy but eventually cleared.

The group, which had been under investigation since 2003, set up ‘Salafist jihadi’ militant cells which recruited and assisted would-be suicide bombers.