The presumed mastermind of the jihadist cell dismantled this week in Belgium remains at large, a Belgian minister said, after arrests in Greece.
Asked if the suspected leader remained on the run after two people were arrested in Athens Saturday in connection with the Belgian probe, Justice Minister Koen Geens told VRT television: "That is indeed the case."
"Last night's arrests did not succeed in nabbing the right person. We are still actively looking for him and I presume we will succeed," he added.
Belgian media have named the suspected leader of the cell uncovered by police Thursday in the eastern town of Verviers as Abdelhamid Abaaoud, a 27-year-old Belgian of Moroccan origin.
Two suspects were shot dead in a fierce gun battle with police during the raid, which smashed a cell plotting to kill Belgian police officers on the street and in police stations, local authorities said.
According to Belgian media, the group's suspected leader Abaaoud spent time fighting alongside the Islamic State group in Syria.
He was already known to security forces after appearing in an Islamic State video, at the wheel of a car transporting mutilated bodies to a mass grave.
Belgium's Flemish-language VTM channel reported that Abaaoud had made calls from Greece to the brother of one of the two heavily-armed suspects killed in Verviers.
A Greek police source said antiterrorism investigators sent DNA samples and fingerprints to Belgium to establish whether Abaaoud was among the suspects arrested in Athens.
Initial reports had put the number of suspects in Greek custody at four but a police source said only two people were arrested, at least one of whom was released without charge Sunday.
A spokesman for the Belgian federal prosecutor's office, Eric Van Der Sypt, said there was "no connection" between the suspects and the Belgian enquiry.
In Belgium itself, 13 people were arrested in connection with the probe, five of whom have been 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.
Furthers searches were made Sunday in the Brussels district of Molenbeek where Abaaoud lived, media reports said.
Two fugitives who left Belgium immediately after the attack were arrested in France.
The arrests across Europe came a week after 17 people were killed in Islamist attacks in Paris, rekindling fears in Europe about the threat posed by young Europeans returning home after fighting alongside extremist 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 jihadist groups.
Of the 335 who have gone to fight -- out of a population of 11 million -- 184 are still there and 50 have been killed, while 101 have returned to Belgium, authorities have said.