The EU is set to strengthen its borders as Frontex warns the bloc has become more vulnerable to militant attacks

The European Union's executive will propose on Wednesday a raft of technical measures to strengthen its external borders as it seeks to tackle both an uncontrolled influx of migrants and security threats following deadly attacks in Paris and Brussels.

The announcement comes a day after Frontex, the EU's border agency, said that Europe had become more vulnerable to militant attacks following 1.82 million illegal border crossings last year.

More than 160 people were killed in the November shooting and bombing attacks in Paris and suicide bombings in Brussels in March.

The deadly strikes, claimed by Islamic State, strengthened the hand of those campaigning for tighter security checks and data sharing against those who warn of the risks of abuse and undermining privacy through enhanced surveillance.

In its proposal on Wednesday, seen by Reuters ahead of official publication, the European Commission said the carnage in Paris and Brussels "brought into sharper focus the need to join up and strengthen the EU's border management, migration and security cooperation."

Europol chief Rob Wainwright highlighted separately on Tuesday an "indirect link" between Europe's migration crisis, which saw more than a million people arriving over the last year, and the Islamist militant threat, saying some militants had used the chaotic migrant influx to sneak in.

Two of the Paris attackers had entered Europe through Leros where they were registered by the Greek authorities after presenting fake Syria identification documents.

"The Paris attacks in November 2015 clearly demonstrated that irregular migratory flows could be used by terrorists to enter the EU," Frontex said in a report.

"With no thorough check or penalties in place for those making such false declarations, there is a risk that some persons representing a security threat to the EU may be taking advantage of this situation."

Frontex, Europol and the European Commission all acknowledge that the irregular, un-organized border crossings have been exploited by foreign terrorists and so-called foreign fighters (European citizens who went to train with terrorist organizations in the Middle East and are being sent back to commit terrorist acts).

"EU citizens are known to have crossed the external border to travel to (Middle East) conflict zones for terrorist purposes and pose a risk upon their return. There is evidence that terrorists have used routes of irregular migration to enter the EU," the Commission said in its proposal.

Communication is key

The EU has a dozen-or-so different sets of fragmented databases for border management and law enforcement that are plagued with gaps and often not inter-operable. Custom authorities' data are held largely separate.

The Commission on Wednesday will therefore set out technical proposals to beef them up and improve the way they communicate with one another, including a joint search interface.

Although not a new idea in general, doing this requires complex measures that pose a host of technical and legal challenges in balancing the need for data and privacy protection with enhanced security.

The Commission also revised a proposal, first made in 2013, for an "Entry-Exit" system for third-country nationals arriving in the EU to "reduce irregular migration by addressing the phenomenon of overstaying and contribute to the fight against terrorism and serious crime".

Under the outline, the new system would be implemented by 2020 to register data of non-EU nationals arriving from outside the bloc, including four fingerprints and a face image.

Scores of Europeans have ventured out to join the ranks of Islamic State and some have come back to the 28-nation EU, including those involved in the Paris attacks.

That stirred discussion on the need to also tighten controls of EU citizens on external borders, but this angle was not included in the Commission's document on Wednesday.

Also mentioned was the so-called PNR - an EU deal on sharing detailed air passenger data that has seen months of wrangling. The Commission said it should be adopted "in the coming weeks" and is crucial in efforts to increase security.

A Frontex report also pointed to the routes used for smuggling weapons, often traded from former conflict regions such as the Western Balkans, where about 800,000 weapons are estimated to be in illegal civilian possession in Bosnia and Herzegovina alone.

A few days before the Paris attack, German police officers discovered pistols, hand grenades, Kalashnikov rifles with ammunition and an explosive agent. The weapons were transported from Montenegro to France in a car of a man probably linked to suspects behind the Paris attacks, Frontex said.

Frontex has also said that the upsurge in detection has also led to a surge in violent incidents along the EU's external borders. People smugglers have threatened border guards and the numbers of people crossing borders en masse have led to violent clashes.