The arrest of five men suspected of links to the Brussels bombings, including the last-known fugitive in last year's Paris attacks, raised new questions about the extent of the Isis cell believed to have carried out the attacks.
After weeks of speculation about a mysterious "man in the hat" who escaped the two Brussels attacks in which three suicide bombers blew themselves up, authorities were checking whether that man was indeed Mohamed Abrini, the last identified suspect at large from the Paris attacks.
Another man arrested in a series of raids, identified as Osama K by Belgian authorities, was linked to the November 13 Paris attacks by French authorities on March 22, hours after the Belgium attacks.
Abrini and Osama K are suspected of playing a role in the two biggest attacks by Isis in Europe over the past year, killing 130 people in Paris and 32 in Brussels. French authorities renewed their call to arrest an armed and dangerous Abrini within hours of the Brussels attacks.
The man walked away from the airport attack, where two suicide bombers blew themselves up, killing 16 people."We are investigating if Abrini can be positively identified as the third person present during the attacks in Brussels National Airport, the so- called 'man in the hat'," said prosecutor Eric Van der Sypt.
Authorities have detained four other men including Osama K, suspected of having contact with the suicide bomber who blew himself up in the Brussels subway the same morning, killing another 16.
Osama K was filmed by security cameras in the City 2 shopping mall when the bags used by the suicide bombers who attacked the airport were bought.
Belgian prosecutors said Abrini's fingerprints and DNA were not only in a Renault Clio used in the Paris attacks, but also in an apartment in the Schaerbeek area of the Belgian capital used by the Brussels bombers.
The detentions were a rare success for Belgian authorities, who have been accused for months of mishandling the investigation. The interior and justice ministers had offered to resign before the detentions.
Despite multiple arrests, Brussels remains under the second-highest terror alert, meaning an attack is considered likely.
Abrini is a 31-year-old Belgian-Moroccan, known as a petty criminal before he was believed to have travelled last summer to Syria, where his younger brother died in 2014 in Isis' notorious francophone brigade.
Abrini had not resurfaced since the emergence of surveillance video placing him in the convoy with the attackers headed to Paris. He had ties to Abdelhamid Abbaoud, the ringleader of the Paris attacks who died in a police standoff on November 18, and is a childhood friend of brothers Salah and Brahim Abdeslam, suspects in the Paris attacks.
Salah Abdeslam is awaiting extradition to France.