* Third man filmed with suicide bombers at airport

* Second bomber believed involved in metro attack-media

* EU interior and justice ministers to meet  

Belgian police were hunting on Thursday for a "third man" filmed with two Islamic State suicide bombers at Brussels Airport as investigators accumulated evidence that the same jihadist network was involved in the deadly Paris attacks last November.

As pressure mounted on Europe to improve cooperation against terrorism, EU interior and justice ministers were to hold emergency talks on a joint response to Tuesday's Brussels bombings, which killed at least 31 people and injured 270.

French Prime Minister Manuel Valls led calls for a "strong European response", but officials say many states, including France, withhold their most cherished data despite a mantra of willingness to share intelligence.

Turkey's president criticised Belgium for failing to track Brahim El Bakraoui, a convicted armed robber whom it deported last year and who blew himself up at the airport on Tuesday an hour before his brother Khalid, a fellow convict, killed about 20 people at Maelbeek metro station in the city centre.

Security sources told Belgian media the other suicide bomber at the airport was Najim Laachraoui, a veteran Belgian Islamist fighter in Syria suspected of making explosive belts for November's Paris attacks, who also detonated a suitcase bomb at the airport.

The third suspect captured on airport security cameras, pushing a baggage trolley into the departures hall alongside Laachraoui and Brahim El Bakraoui, is now the target of police searches. The bespectacled man wearing a cream jacket and a black hat fled the scene, federal prosecutors said, and a third suitcase bomb, the biggest of the three, exploded later as bomb disposal experts were clearing the area.

Public broadcaster RTBF said investigators now believed a second bomber was involved in the metro attack close to European Commission headquarters. The man was spotted on security cameras carrying a heavy bag, but his identity was unknown and it was not clear if he had died or escaped.

US criticism

US Defence Secretary Ash Carter said the bloodshed in the capital of the European Union, not far from Nato headquarters, showed Washington's European allies should do more to fight Islamic State alongside American efforts in the Middle East.

"The Brussels event is going to further signify to Europeans that, as we have been accelerating our campaign to defeat ISIL in Syria and Iraq and elsewhere, they need to accelerate their efforts and join us," Carter told CNN.

Democratic US presidential candidate Hillary Clinton criticised the lack of cooperation among European countries, saying the EU lacked a system for exchanging air passenger data or a joint intelligence centre to share information.

Casualties came from about 40 nations, drawing an international outpouring of support for the cosmopolitan city during three days of mourning.

Washington announced that Secretary of State John Kerry would visit Belgium on Friday.

The Belgian government deflected criticism from Turkey's President Tayyip Erdogan, saying the elder Bakraoui brother, 29, had not been deported to Belgium but to the Netherlands.

Officials have said that, as in the case of one of the Paris suicide bombers, they cannot detain militant suspects expelled from Turkey without evidence that they have committed a crime.

Brahim El Bakraoui was detained near the Syrian border and expelled last July. "Belgium ignored our warning that this person is a foreign fighter," Erdogan said.

Flemish public broadcaster VRT said the bomber had been released from a Belgian prison in 2014 after serving four years of a 10-year sentence for armed robbery. He skipped two probation meetings last June and was ordered to return to prison in August. But police could not find him.

The case highlighted the problem Belgium has faced with some 300 locals who have fought in Syria, the biggest contingent from Europe in relation to its national population of 11mn.

Foreign Minister Didier Reynders, leading efforts to counter international criticism of Belgian policies toward containing violent extremists among its Muslim community, which makes up about 5% of the population, said security had to be balanced with civil rights.

On Tuesday, US Republican presidential front-runner Donald Trump suggested torture could be used on militant suspects.

Belgium, which has deployed warplanes to coalition operations in the Middle East, has increased spending on police and intelligence services since 130 people were killed in Paris on November 13 in attacks planned by Brussels-based militants.

‘Stop lecturing Belgium’

As Brussels struggled to return to normal, its airport remained shut until at least Saturday, with the departure hall sealed off by investigators.

Travellers on the busy Easter weekend were diverted to Antwerp, Liege and the northern French city of Lille.

Brussels Airlines advised passengers to arrive up to three hours before their flight because of new security measures. There were long lines outside the terminal in Liege as people waited in the rain to put their baggage through outdoor scanners, VRT reported.

As Belgians struggled to cope with the shock of the attacks and a torrent of international criticism of their security services, European Commission President Jean-Claude Juncker jumped to the country's defence, dismissing charges that Belgium is a "failed state".

"Let he who is without sin cast the first stone," Juncker told Flemish daily De Standaard. "There was terrorism in Britain and in Germany in the 1970s and 1980. There was terrorism in Spain, in Italy and much more recently in France. People should stop lecturing Belgium."

Another minute's silence was planned across Belgium for Thursday. Commuters on their way to work stopped at an improvised shrine on the square outside the Brussels bourse to light candles or deposit flowers.

Belgium's crisis coordination centre kept the level of security alert at the maximum as the manhunt continued.

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