The international manhunt for the Brussels suicide bombers' accomplice is deepening as Belgium enters its second day of mourning over the terror attacks that shook Europe.
Some 34 people are known to have died, while at least 198 - including two Britons - are injured.
Others have been reported missing following the double blast in the Belgian capital's Zaventem Airport, and the subsequent explosion on a subway train at Maelbeek Metro station. Among them was Brussels commuter David Dixon, originally from Hartlepool, who failed to arrive at work on Tuesday morning.
Investigators are focusing on whether CCTV footage captured moments before the airport blasts shows two of the three suspected terrorists wearing single gloves to secrete detonators. It came as Zaventem's mayor said the explosives were stowed in their luggage and detonated before reaching the security gate.
David Cameron is expected to chair a second meeting of the Government's emergency Cobra committee in response to the attacks, for which Islamic State (IS) militants have claimed responsibility.
It came as transport terminals across the UK and Europe ramped up security measures following in the wake of the atrocities.
The attacks, condemned as "blind, violent and cowardly" by Belgian prime minister Charles Michel, happened four days after the arrest of Salah Abdeslam, who plotted November's massacre in Paris. Detectives are yet to rule out a direct link between the attacks.
As night fell on Brussels, Mr Michel showed solidarity with Belgians by lighting a candle at a vigil at Place de la Bourse, the city's stock exchange building.
He told a press conference earlier that the atrocities had killed people whose lives "were in full course".
He said: "The lives of people who were most likely travelling without a care in the world, going to work or to school, lives that have been broken by extremism."
King Philippe of Belgium led the calls for calm as Belgian police issued an image of the fugitive, one of three seen pushing luggage trolleys through Zaventem airport moments before two bombs exploded.
A third bomb was deactivated at the airport hours after the initial attack - which was followed by a bomb blast on a Metro train in the city centre as terrorists inflicted a new outrage on a European capital.
Prosecutor Frederic Van Leeuw said the three people captured on camera at the airport were the chief suspects - with two of them "probably committing a suicide attack".
He said: "The third - dressed in a white jacket and wearing a hat - is actively sought.
"Various departments and experts are currently in various crime scenes. This will take place for many hours to come.
"Due to the violence of the attacks, this investigation is particularly difficult.
"Various operations are ongoing across the country and several witnesses have been heard."
Images of passengers climbing from a train into a smoke-filled tunnel near Maelbeek station were reminiscent of scenes following the July 7 attacks in London.
Other footage showed the injured from the Metro being treated in the street, while at the airport people could be seen fleeing in terror in video footage shot from an airport car park.
International leaders united in support for Belgium, with Mr Cameron branding the atrocities "appalling" and US president Barack Obama condemning the "outrageous attacks against innocent people".
The Prime Minister's official spokeswoman said Britain was sending a team of specialist police officers to the city to assist with the investigation, while the Foreign Office said it was no longer advising against travelling to Brussels.
French prime minister Manuel Valls said: "We are at war. In Europe we have been subjected to acts of war for several months."