The aftermath in the departures hall at Brussels Zaventem airport following the explosions

More than 30 people were killed and dozens more injured in explosions at Brussels airport and a metro station on Tuesday.

Twin blasts struck the main terminal of Zaventem international airport, in the north-east of the city.

Another explosion hit the Maelbeek metro station in the city centre, close to several European Union institutions.

The so-called Islamic State group said it was behind the attacks.

They came four days after the capture in Brussels of Salah Abdeslam, the main suspect in the jihadist attacks in Paris on 13 November 2015.

Who carried out the attacks?

Two of the men who carried out the attacks have been named by Belgian media as brothers Khalid and Brahim el-Bakraoui.

The RTBF broadcaster said the pair were known to police. It is believed at least one of the brothers was among three suspects seen in a CCTV image at Zaventem airport.

A CCTV image of three men said to be suspected of being behind the airport attacks has emerged

Police in Brussels issued a wanted notice for the man pictured wearing a hat, and urged the public to contact them if they recognised him. One Belgian media outlet has named him as Najim Laachraoui - named earlier in the week as an accomplice of Abdeslam.

The so-called Islamic State group said it was behind the attacks.

In a statement released on Tuesday afternoon via the IS-linked Amaq news agency, the group described the attacks as "a series of bombings with explosive belts and devices".

The airport attack

Two explosions, moments apart, tore through the check-in area of Zaventem airport at about 08:00 local time (07:00 GMT) on Tuesday.

An eyewitness reported hearing gunshots and shouts in Arabic just before the explosions.

The Belgian federal prosecutor said one of the blasts was "likely" to have been a suicide bomb.

One witness said people ran from the site of the first blast, only to be caught in the second, near the main entrance.

The metro station attack

Just over an hour later, a further blast happened at the Maelbeek metro station in the city centre, close to several EU institutions.

A three-carriage train was just leaving the station in the direction of Arts-Loi, the next stop a short distance away, when the blast happened, according to Brussels transport operator STIB.

The bomb was apparently detonated in the middle carriage, which was running along the platform at the time. The driver immediately halted the train and evacuated the first and last carriages.

How many people have been killed?

More than 30 people have died in the three explosions but the total death toll remains unconfirmed.

The Belgian health minister said 11 were killed and 81 injured in the airport blasts.

The metro explosion killed at least 20 people, the Brussels mayor told local media.

At least a further 100 people have been injured, 17 of them seriously.

Earlier, Belgian Prime Minister Charles Michel told a news conference "there aremany dead, many injured".

"What we feared, has happened," he added. "We realise we face a tragic moment. We have to be calm and show solidarity."

The investigation

The anti-terror section of Belgium's federal prosecutor's office has opened a criminal investigation.

In a statement, the prosecutor's office said police had conducted raids in the Schaerbeek neighbourhood of Brussels on Tuesday evening and found a nail bomb, chemical products and an Islamic State flag.

Earlier on Tuesday, police were reported to have found an unexploded suicide vest at Brussels airport as well as a Kalashnikov assault rifle.

Is Brussels safe?

Belgium raised its terror threat to its highest level following Tuesday's attacks.

The national crisis centre urged people to "stay where you are" and instructed schools to keep children inside. This was eased at 16:00 local time on Tuesday.

Soldiers were deployed across Brussels in the hours after the two deadly attacks

Is transport still running?

Brussels Zaventem airport closed after the attacks, with all flights diverted elsewhere. Officials say it will remain closed on Wednesday.

The city's entire metro rail system was shut down after the explosion at Maelbeek station. Some tram and bus services were also halted but public transport was restarted at 16:00 local time, with some metro lines reopening.

Eurostar suspended its high-speed rail service to and from Brussels initially but a limited service is now running.

Why has Brussels been attacked?

Belgium's Interior Minister Jan Jambon said on Monday that there was a threat from revenge attacks after the capture of Salah Abdeslam.

Abdeslam, a suspect in last year's Paris attacks, was wounded and arrested in a police raid on an apartment in the Molenbeek suburb of Brussels last week.

The Belgian-born French national is said to be co-operating with police and is fighting extradition to France.

Mr Jambon told Belgian radio: "We know that stopping one cell can... push others into action. We are aware of it in this case."

How have other countries reacted?

Security measures have been stepped up in western European countries following the attacks.

French Interior Minister Bernard Cazeneuve said an extra 1,600 police officers had been deployed to train stations, airports and border crossings. France has been on alert since 130 people were killed in attacks in Paris last November.

British airports and transport hubs are also increasing security as a precaution and Prime Minister David Cameron is convening the UK government's Cobra emergency committee, which brings together ministers, police and intelligence officers.

The UK's official terrorist threat level remains unchanged at "severe," the second-highest level on a five-point scale, meaning an attack is highly likely.

German authorities have stepped up security measures at airports, train stations and the borders with Belgium, France, the Netherlands and Luxembourg, a spokesman for the federal police said.

Source: www.bbc.co.uk