Police busted on Tuesday a Chechnya-linked Islamist network plotting an attack on Belgium and rounded up another extremist group suspected of recruiting jihad fighters, amid heightened terrorism fears in Europe.
Authorities detained 11 suspects in Belgium, the Netherlands and Germany to break up a Chechnya-linked network planning to strike Belgium, arresting seven of them in the Belgian port city of Antwerp, home to both large Jewish and Muslim communities.
Hours later, Belgian officials announced the detention of around 15 people in Brussels in connection with a probe into a group suspected of looking for would-be "jihadists" ready to join the battles in Iraq and Afghanistan.
Dutch prosecutors said the arrests in Amsterdam involved three Dutch nationals in their twenties and that the men would soon be extradited to Belgium.
In Germany, a 31-year-old Russian national was arrested in Aachen on suspicion of recruiting fighters for the Caucasian republic of Chechnya, the Federal Crime Office (BKA) said.
"There were plans aimed at committing an attack in Belgium by an international terrorist group using for this purpose an extremist internet site, Ansar Al Mujahideen," said the Belgian prosecutor's office.
Belgian investigators had led an international inquiry from 2009 into a suspect network largely based in Antwerp.
"The target of the attack was not yet specifically determined," the prosecutor's office added, but there were "sufficient facts" to justify the raids.
No extra security measures will be enforced in Belgium, home to the European Union and NATO, a spokesman for the government's crisis centre said.
Those arrested -- of Belgian, Dutch, Moroccan and Russian (Chechen origin) nationalities -- are also suspected of recruiting "jihadist candidates" and financing "a Chechen terrorist organisation, the Caucasus Emirate".
The detainees go before an investigating magistrate later Tuesday who will decide whether to keep them behind bars pending charges.
Belgian authorities said several other people had already been arrested in Spain, Morocco and Saudi Arabia as part of the same probe, conducted with other countries and the EU's judicial cooperation unit Eurojust.
The Belgian prosecutor's office announced later the arrest of "around 15 people" following searches in homes across Brussels in a pre-dawn operation aimed at "dismantling a group with terrorist characteristics".
The arrests followed a three-year investigation into people connected with a Belgian Islamic centre, it said. Foreign police services cooperated in the probe.
Europe has been on high alert for several weeks over heightened fears of terrorist attacks.
Western security officials have warned that Al-Qaeda may be planning attacks in Europe similar to those that struck the Indian city of Mumbai in 2008.
On Monday the cupola of Germany's Reichstag parliament building was closed until further notice to visitors after media reports said the popular tourist site was a potential target for Islamist extremists.
Germany's interior ministry said Tuesday's arrests were not linked to recent security threats in the country.
In Denmark, intelligence officials warned of new information "that foreign-based terrorist groups will try to send terrorists to Denmark to stage attacks" and urged police to be "extremely vigilant" ahead of Christmas.
The United States issued on October 3 a travel alert for its citizenstravelling in Europe, citing the risk of potential terrorist attacks on transportation systems and tourist attractions.