Governments and security services across Western Europe have stepped up their antiterrorist efforts in the wake of the recent spate of hijackings and bombings and have reported some successes.
Yesterday, Belgian police announced the arrests of two Arabs suspected of planning an attack on the Brussels airport similar to last week's airport attacks by Palestinian terrorists in Rome and Vienna.
The upsurge of violent incidents has led to public pressure on Western European governments to tighten controls on travelers from the Middle East.
The arrests in Belgium were made after the two Arabs arrived at Brussels airport on a flight from Athens last Saturday. They were placed under surveillance after the name of one of them showed up in a police computer as having undergone terrorist training in Lebanon.
Police tailed the two men, together with a Belgian acquaintance who greeted them at the airport, to the village of Hasselt, about 60 miles from Brussels.
There police raided a video shop owned by the Belgian, where they discovered an arms cache that they said included a submachine gun, four rifles, handguns, detonators, several hundred rounds of ammunition, hand grenades and 42 pounds of explosives.
Belgian officials refused to give the names of the two Arab suspects but the state radio said that they appeared to have been planning an attack on the Brussels airport similar to those in Rome and Vienna.
Security at major European airports has been increased as a result of the Rome and Vienna attacks. A state of maximum alert was declared at Madrid airport following reports that it was targeted for attack, while British Army units were involved in an antiterrorist exercise at London's Heathrow airport earlier this week.
Public pressure on governments for action has been particularly apparent in countries such as Greece and Italy, which have traditionally cultivated good relations with Arab countries.
Greek police launched a sweep of hotels in Athens this week, looking for Arabs with forged passports or expired residence permits.
Eight Palestinians were detained but later released and expelled from the country after a government spokesman said there was no evidence that they had been planning a terrorist attack.
The Greek government signed an agreement earlier this week with the Palestine Liberation Organization pledging joint action against terrorists. Athens airport was the starting point for last year's bloodiest hijacking incidents involving TWA and Egyptair planes.
At Rome's Leonardo da Vinci Airport, scene of last Friday's attack whose 16th victim died today, airport workers staged a symbolic three-hour strike today to press demands for improved security. The protesters want metal detectors installed at the main entrance to the airport in addition to the surveillance measures already in effect.
Although there is no evidence of a direct connection among these recent arrests and detentions, they reflected the increased police surveillance of potential terrorist suspects as they cross national frontiers.
In the past, the absence of rigorous border restrictions and the difficulties of coordinating the work of different police forces have eased the task of terrorists.
This week, in another countermove, French officials claimed to have foiled a plot to bomb a Paris synagogue.
Two Portuguese citizens and an Egyptian were arrested by France's domestic counterintelligence agency after arriving from Madrid with false Spanish passports. French officials later said that bomb-making equipment had been discovered in their hotel room along with a map of Paris that suggested their target was the synagogue on the Rue Copernic in the city's 16th district.
The synagogue was the scene of a 1980 terrorist attack that killed four persons. No one claimed responsibility for that attack. In Spain, meanwhile, officials revealed that three Libyan officials were quietly expelled last month when police heard that they were preparing the murder of a prominent Libyan political exile.
According to reports from Madrid, the expulsion of the Libyan officials was made possible as the result of cooperation between the police and military intelligence.
Spanish authorities are believed to have been keeping a special watch on the Libyan embassy following claims in the press that Libya is providing assistance to the Basque separatist organization ETA (Basque Homeland and Freedom).