* Many will make treacherous Mediterranean crossing

* Chaos in Libya gives people smugglers free hand

* Border agency boss seeking more resources

By Christian Lowe

WARSAW, Feb 17 (Reuters) - A record number of migrants look set to flow into Europe this year, with human traffickers becoming increasingly aggressive as they take advantage of chaos in Africa and the Middle East, the EU borders chief said.

Many asylum seekers and illegal immigrants are reaching Europe via the Mediterranean sea, with hundreds dying during the perilous crossing, said Fabrice Leggeri, executive director of Frontex, the European Union's border cooperation agency.

Libya's plunge into anarchy has created an ideal environment for traffickers, who pack people fleeing war and poverty in the Arab world and sub-Saharan African onto rickety boats that set sail for Europe -- mainly aiming for nearby Italy.

In an interview at the Warsaw headquarters of Frontex, Leggeri said the numbers since Jan. 1 of what his agency terms "irregular crossings" into Europe at all border points was the highest ever recorded.

An official put the number at more than 5,600, despite winter storms and cold that normally deter the human smugglers.

Asked if that meant 2015 would be a record year, Leggeri said: "Yes, if the current trend is confirmed."

In 2014, there were approximately 300,000 irregular crossings into the European Union, with U.N. data showing at least 218,000 people entering via the Mediterranean. The other major route for migrants was overland from the Middle East into the western Balkans and onto the EU, officials said.

"There are obvious reasons: because of the geo-political situation in Syria and the Middle East, because in Libya one can say there is a failed state and there is no government able to have effective control of the territory, which makes it easier for organised crime to flourish there."

Leggeri said traffickers were becoming more aggressive.

In one case this month, smugglers pulled out guns to threaten an Italian coastguard crew which was trying to tow a wooden vessel filled with migrants into port. The traffickers, he said, wanted the boat back so they could use it again.

Frontex is in charge of an EU coastguard mission patrolling the Mediterranean, dubbed Operation Triton, which started work last November just as Italy wound down a much larger programme, Mare Nostrum, that rescued more than 100,000 migrants in 2014.

The Mediterranean crossing claimed an estimated 3,300 lives last year, and earlier this month more than 300 people are believed to have died after leaving Libya in inflatable rafts.

The United Nation's refugee agency, the UNHCR, says Operation Triton is woefully inadequate, and urged Europe to take a new approach.

Leggeri said Operation Triton, which had been planned to run only until the end of January, would now carry on throughout the year, adding that it had already helped save up to 9,000 people.

The International Organization for Migration said on Tuesday that some 3,800 migrants had been rescued from the Mediterranean since last Friday alone.

Leggeri said he had put out a call to EU member states to provide the vessels and aircraft needed to keep the operation going. Frontex has no operational resources of its own.

Triton currently employs nine boats and two aircraft.

"We have to get ready and when I say 'we' it's Frontex but also the member states. We have to be prepared to face a very difficult year," he said. (Editing by Crispian Balmer)