The appeal came after investigators freed a suspect taken into custody and initially charged with participating in a terrorist attack.
But the man, Faysal Cheffou - who resembles the attacker shown in the airport surveillance image and was identified by a taxi driver who took them to the airport - refused to answer questions, and there was not enough evidence to hold him, the prosecutor's office said. Prosecutors will decide later in the investigation whether to proceed with any charges against him, officials said.
READ: Belgium releases sole suspect charged over Brussels attacks
READ: Belgian police release video footage of third airport suspect
The release of Cheffou, who in the past has publicly promoted extreme Islamist beliefs in Brussels, reopened the manhunt for the "man in white" suspect and raised further questions about the extent of the network behind last week's bloodshed.
In the video, the third airport bombing suspect is shown in a dark floppy hat, glasses, a goatee and white jacket pushing a luggage cart with a black suitcase on it shortly before bombs exploded March 22. A photo from the video was made public shortly after the attacks, but the new video gives a slightly better view.
One bomb - believed to be the one wheeled by the man - did not detonate in last Tuesday's carnage, which began at the airport and was followed by a suicide blast in a busy metro station.
Meanwhile, police across Europe widened anti-terrorism crackdowns as prosecutors in Belgium charged three other people suspected of having links to militant networks, adding further to signs that the multi-nation probes were moving rapidly beyond last week's bombings in Brussels.
Yet even as the authorities chased new leads, there was still more reckoning from last Tuesday's attacks claimed by the Islamic State.
Belgium's health minister raised the death toll to 35, not counting three suicide bombers. About 300 people were injured, of whom 96 remain hospitalized, according to the Belgium Crisis Center.
Nearly half of those killed were foreign nationals, including at least four Americans. The Belgian Foreign Ministry said not all of the wounded have been identified because some remain comatose.
In Brussels, the federal prosecutor identified the three people charged with "participation in the activities of a terrorist group" only as Yassine A., Mohamed B. and Aboubaker O. They were among nine people detained Sunday morning by police for questioning; the rest have been released.
It was not immediately clear whether the latest suspects played roles in planning the suicide blasts at Brussels Airport and a metro station. But the police sweeps across the European Union suggested moves aimed at heading off possible new attacks.
The raids and arrests added to a picture of multinational networks reaching far beyond the Islamic State strongholds in Iraq and Syria, where the group recently has suffered setbacks.
On Monday, Dutch police said they arrested three other men allegedly linked to terrorism planning. A day earlier, Dutch authorities captured a 32-year-old French citizen in Rotterdam who was suspected of ties to an apparent foiled attack in France last week. They gave his name only as Anis B.
Wim de Bruin, a spokesman for the Dutch prosecutor's office, said in an interview that police found mobile phones, SIM cards, ammunition, money and drugs when capturing him.
Dutch police said two of the three other detained men, age 43 and 47, were of Algerian origin. No information was released about the third suspect. De Bruin said all three were arrested while police were looking for Anis B. He said none of them would be extradited to France.
Italian police, meanwhile, were holding Djamal Eddine Ouali, a 40-year-old Algerian suspected of having provided false documents to the Islamic State militants behind the attacks in Paris and Brussels. He was arrested over the weekend.
In central Brussels, tensions that marred a memorial event Sunday threatened to recur.
On Monday, a group called Identity Generation spread fliers calling for a demonstration with the slogan "Expel the Islamists" on April 2 in Molenbeek, an overwhelmingly Muslim middle-class neighborhood in Brussels and a hub for some of the suspected plotters in last year's Paris attacks.
In Saudi Arabia's capital, Riyadh, senior officials hosted the first meeting of a newly formed Islamic military coalition aimed at combating terrorism, the state-run Saudi Press Agency reported. Saudi Arabia and some of its Arab partners in the Persian Gulf have come under increasing pressure from Western allies to target private groups and mosques accused of raising funds and other support for radical Islamist factions outside the region.
The spokesman of the alliance, Saudi Brig. Gen. Ahmed Asiri, said the talks among the 34-nation group included ways to "dry up terrorists' resources," the news agency reported, but he gave no further details on possible strategies.
