MILAN (REUTERS) - After the truck attack that killed 84 people in Nice, Italy tightened controls at four border crossings with France over fears an assailant could sneak across onto Italian soil.

The rapid action reflected growing Italian concern about weak cooperation on security matters in the European Union after a spate of deadly attacks - in France, Belgium and now Germany.

Those concerns have become so great that Italian officials have started voicing their alarm in public, a rare step for such officials in Italy.

"What happened in Nice, and in a sense also what happened in Munich, only reinforces what I am saying: that we need to focus everything on prevention and share all useful information," said Claudio Galzerano, a senior official with Italian anti-terrorism police in charge of international cooperation.

Even before the July 14 attack in Nice, 35km from the Italian border, three senior Italian security officials told Reuters they were worried about the reluctance of some national police forces to share information with the EU's policing agency, Europol.

"If Europol isn't fed with more data from member countries, it will remain a beautiful but empty box," Galzerano said, adding that information on potentially violent, mentally ill people should also be shared with and among police forces.

Since Friday, two assailants with histories of mental illness launched separate attacks in Germany: a German-Iranian gunman who killed nine people in a Munich shopping mall and a Syrian suicide bomber who injured 12 outside a music festival.

Likening counter-terrorism to the team sport of soccer, Galzerano said: "If you stretch your defence too thin, the attacking players can score a goal more easily."

Asked about Galzerano's remarks, a spokesperson from Europol said the organisation provided "the kind of cooperation Europe needs in the fight against organised crime and terrorism".

Although it is rare for top Italian security officials to comment so openly in public, Galzerano's remarks echo those of officials in other European countries.

Concerns have been growing since January last year when 17 people were killed in Islamist attacks on French satirical weekly Charlie Hebdo and a Jewish supermarket. Last November suicide bombings and shootings killed 130 in Paris, followed in March by the Brussels metro and airport attacks which killed 32.

In February, The Netherlands, then holder of the EU presidency, called for greater sharing of intelligence data.

In other signs of concern, a French parliamentary investigation found multiple intelligence failures before the Paris attacks and called for the creation of a counter-terrorism agency to prevent further violence.

Some of the Paris attackers had been on the radar of authorities in various countries. The Islamic State in Iraq and Syria (ISIS) suicide bombers who attacked Brussels airport two months after the Dutch plea were suspected of having links to the Paris killings.

"Often, they (police) show enormous resistance in sharing, for investigative purposes, information and data that is really useful," said one of Italy's most prominent counter-terrorism investigators, Turin-based prosecutor Armando Spataro.

CHARLIE HEBDO

Spataro said bilateral cooperation worked well with some countries, such as Germany and Spain, but broke down at times with other EU partners, such as after the attacks on Charlie Hebdo and the Jewish supermarket.

A few days after those attacks, two people with suspected links to the Belgium-based cell behind the attacks were on their way to Italy when they were stopped by French customs officials at Frejus, at the request of Belgian authorities, Spataro said.

Italian authorities immediately asked Belgium and France for information on why they were travelling to Italy, he said. "But we did not receive a response for a couple of weeks,"Spataro added, declining to give more details on the case.

Asked for comment, the French justice ministry said requests were handled on a case by case basis between the legal services directly concerned in each country.

Italy has avoided a major terror attack, though there are fears in Rome that ISIS, under pressure on the battle fields of Syria and Iraq, could attempt to mount strikes on Italian soil, especially in the capital, or at the Vatican.

Italy has been a major gateway for Middle East and African migrants seeking asylum in Europe, including from regions under the control of militant jihadists.

The controls installed after the Nice attacks remain in place at three road crossings into France and at the Ventimiglia train link.

In April, Italian police arrested four Moroccans suspected of conspiring to join ISIS. Court documents showed they were among a group that had been discussing possible attacks on the Vatican and the Israeli embassy in Rome.

Spataro said foreign police and judicial investigators were kept in the dark by their own nations' intelligence agencies, while several EU databases, not just Europol, were neglected.

A source close to Italian intelligence said the EU's Schengen Information System, a wanted-persons database for 26 nations of the Schengen open-borders zone, was also unreliable. "Each country has its individual way to put data into the system," said the source.

A spokesman for the European Commission, the EU executive, said the EU was working to improve the system, and the number of alerts for checks at borders had tripled since 2013, a sign it was working.