At least four people have been arrested in Athens as part of a probe into a jihadist cell that was dismantled in Belgium this week before it could carry out any attacks.
Greece's anti-terror police were seeking to determine whether those arrested included Abdelhamid Abaaoud.
Mr Abaaoud, 27, is suspected to be the mastermind of the cell who according to media reports may have been planning the foiled attacks from Greece.
The arrests took place in the Pangrati district of the Greek capital in the middle of the day.
Several mobile phones were also seized.
European nations have arrested dozens of Islamist terror suspects in the wake of the Belgian anti-terror raids, during which two suspects were killed.
Belgium said the cell was planning to kill police officers.
Mr Abaaoud, a Belgian of Moroccan descent, is a notorious jihadist who spent time in Syria.
His alleged involvement comes at a time of heightened fears in Europe about the threat posed by young Europeans returning home after fighting alongside extremist groups in the Middle East.
Meanwhile, Belgium has begun deploying hundreds of troops to patrol the streets after security forces smashed a suspected Islamist "terrorist" cell planning to kill police officers.
Up to 300 soldiers will be deployed in the capital Brussels and the northern city of Anvers, which has a large Jewish population, Prime Minister Charles Michel's office said in a statement.
The soldiers could also eventually be deployed to the industrial eastern city of Verviers.
That was where security forces killed two suspected Islamists in a huge raid on an alleged jihadist cell planning to attack police.
The Belgian raid came a week after Islamist attacks in and around Paris killed 17 people.
Those attacks rekindled fears in Europe about the threat posed by young Europeans returning home after fighting alongside extremist groups in the Middle East.
Armed police have also been deployed in France and Germany.
Following the raid in Verviers, Belgian police arrested 13 people during a series of raids across the country.
Five of these people were later charged with "participating in the activities of a terrorist group".
Belgian prosecutors said there were no immediate links with last week's attacks in Paris on the Charlie Hebdo satirical magazine, a Jewish supermarket and a policewoman, the country's worst attacks in half a century.
