Nearly 30,000 suspected people smugglers have been identified by European authorities since the start of the year.

The figure was disclosed by the head of the EU's law enforcement agency as he told the Press Association criminal activity is at "very high" levels as gangs attempt to exploit the migrant crisis.

Rob Wainwright, director of Europol, said criminal networks are "agile", adopting new tactics such using social media to "recruit" victims.

The UK government has repeatedly highlighted the problem of trafficking gangs, a message repeated today as the European migrant crisis continued.

David Cameron said: "I would say the people most responsible are President Assad in Syria and the butchers of Isil and the criminal gangs that are running this terrible trade in people and we need to be tough on them at the same time."

Tackling the gangs has emerged as a "top priority" for Europol in recent years, Mr Wainwright said.

He said: "Our job is to try and do something about the criminal gangs that are exploiting those conditions and are responsible for exacerbating the problem by recruiting would-be migrants in the first place, giving them false promises about how they can secure their journey to Europe and making an awful lot of money out of it in the process."

A dedicated intelligence project involving all member states has been established to target the perpetrators.

Mr Wainwright said: "Since the start of this year alone we have opened up 1,400 new cases for investigation of facilitators.

"We've identified in those cases almost 30,000 suspected people smugglers at different chains, different levels of criminal syndicates."

He said the cases were initiated by national authorities and sometimes triggered by Europol.

"All of them with cross-border elements, so involving at least two countries, many of them involving multiple countries, and at different levels of scale," he said.

He said Europol is playing an important role in helping the police community across Europe "upgrade" its response to the gangs involved.

"If we can make a serious inroad on that then of course it helps to ease the wider pressures involved," Mr Wainwright added.

"The numbers of migrants are at unprecedented levels and the level of criminal activity equally seems to be at very high levels."

Police are dealing with enterprising, medium-sized criminal groups that are "quite agile in operating in different countries", he said, adding that they are employing new tactics such as "using social media to recruit their victims".

He said: "We are making a sizeable impact on their work."

Europol has set up a dedicated cell in Sicily to improve intelligence about Mediterranean trafficking operations on the frontline.

Mr Wainwright said: "Most of our work is concerned with what we call the secondary distribution of migrants and refugees.

"After they've come through the external border and as they make their journey across European countries."

Fears have been raised that Islamic State - also known as Isil - may seek to take advantage of the migrant crisis to smuggle fighters into Europe. Mr Wainwright said there is no evidence of any such "systematic exploitation".

Last month UK Border Force boss Philip Duffy warned that trafficking gangs are attempting to smuggle migrants to the UK to commit crime.