No link has been established between at least four people arrested by Greek police and a cell broken up this week in Belgium, the Belgian prosecutor's office said.
"There is no connection between these people and the enquiry" in Belgium, Eric Van Der Sypt, spokesman for the federal prosecutor's office, said on Sunday, refuting reports that the two cases were linked.
A Greek police source said investigators had sent DNA evidence and fingerprints to Belgium to establish whether Abdelhamid Abaaoud, the 27-year-old suspected mastermind of the Belgian cell, was among the four suspects.
Belgian authorities said the group targeted in a police raid on Thursday in the eastern town of Verviers, in which two suspects were killed, was plotting to kill Belgian police officers.
The federal prosecutor's office has refused to comment on local media reports that Abaaoud, a Belgian national of Moroccan origin, planned the foiled attacks from Greece or Turkey.
The reports said he made calls from Greece to the brother of one of the two suspects killed in the shootout with police in Verviers.
According to Belgian media, Abaaoud spent time fighting alongside the Islamic State of Iraq and the Levant (ISIL) group in Syria.
He was already known to security forces after appearing in an ISIL video, at the wheel of a car transporting mutilated bodies to a mass grave.
He is also known as the older brother of a 13-year-old boy dubbed Syria's youngest foreign fighter by British media after photos surfaced of him posing with weapons.
Thirteen people were arrested across Belgium in connection with the Verviers cell, five of whom were later charged with "participating in the activities of a terrorist group".
Weapons, bomb-making materials, police uniforms and fake documents were found during searches of their homes. Two fugitives who left Belgium immediately after the attack have been arrested in France.
The Belgium raid came a week after attacks in and around Paris killed 17 people, rekindling fears in Europe about the threat posed by young Europeans returning home after fighting alongside armed groups in the Middle East.
Belgium estimates that 335 of its people have gone to fight in Syria and Iraq in the last few years - making it the European country with the highest proportion of nationals enlisted with Middle Eastern armed groups.