Brussels attacks: What happened and what do we know so far?
Hundreds of people are gathering in the centre of Brussels to pray and mourn for the victims of the terror attacks on the city on Tuesday.
Three bombings in the capital city of Belgium have resulted in at least 31 deaths and 250 people injured, according to provisional figures from the Belgian government's crisis centre.
So what do we know so far?
At about 8am on Tuesday two explosions, just moments apart, rocked the main terminal of Zaventem international airport, in the north-east of the city.
At least 12 people were killed and 100 injured at the airport, a busy European transport hub.
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The blast blew out windows, created a lot of smoke and caused parts of the ceiling to fall.
About an hour later a third blast hit the Maelbeek metro station, located near the European Union headquarters, killing about 20 people and leaving around 130 people with injuries.
It struck the middle carriage of a three-carriage train while it was moving away from the platform, BBC reported.
Is there a man hunt?
Yes, the police have released CCTV images of three men in the airport. The Federal Prosecutor, Frederic Van Leeuw, said at a press conference that two of the three men "very likely committed a suicide attack."
The third man is being hunted by Belgian security forces and a wanted notice has been issued.
He was seen running away from the airport after the blasts, Van Leeuw said.
The three suspected attackers arrived in taxis and had their bombs in their luggage, the local mayor Francis Vermeiren told AFP news agency.
"They put their suitcases on trolleys, the first two bombs exploded. The third also put his on a trolley but he must have panicked, it did not explode."
Police have been carrying out raids in the Schaerbeek neighbourhood and found a nail bomb and Isis flag.
Islamic State claimed responsibility for the attacks.
Is Brussels safe then?
The city has raised its terror threat to the highest level following the blasts. The airport is closed and will remain that way for at least another 24 hours.
Most public transport was shut down after the attacks, but tram and bus routes were restarted at 4pm on Tuesday, local time, and some metro lines also reopened.
The Eurostar train has also resumed its service from London to Brussels.
However most countries - including New Zealand - are telling people to only travel to the country if necessary. The Ministry of Foreign Affairs and Trade has upgraded its travel advisory for Belgium to high risk and urged anyone New Zealanders in the country to register their details.
So should I cancel my up-coming European holiday?
The Ministry of Foreign Affairs and Trade issues advisories about the danger levels of travelling to overseas countries.
After the attacks the travel advisory for Belgium has been updated to "high risk to security" due to the threat of terrorism and MFAT said it advised against all tourist and other non-essential travel to the country.
Keep an eye on the MFAT travel advisories for an update on the threat level and register on Safe Travel as being in Belgium if you are planning to go.
Who claimed responsibility?
Islamic State have claimed responsibility, posting on an Isis-affiliated news agency that "fighters carried out a series of bombings with explosive belts and devices, targeting an airport and a central metro station in the centre of the Belgian capital Brussels".
A statement said Belgium was a country "participating in the international coalition against the Islamic State".
So why did Islamic State target Brussels?
The city is the location of the headquarters of the European Union and NATO, which makes it a high-profile target.
Belgium has also been struggling with increasing numbers of radical Islamists and has a high per-capita number of citizens fighting for IS in Syria and Iraq, the BBC states.
Many of the bombers and gunmen from the November Paris attacks were from the Brussels suburb of Molenbeek and according to police the attacks were planned in the city.
The main suspect in the Paris attacks, Salah Abdeslam, escaped to Belgium the day after and managed to evade capture until March 18 when he was captured by police in Molenbeek.
After the arrest, the authorities warned of possible attacks, although it is too early to directly connect the suicide attacks to the arrest of Abdeslam, the only known survivor from the group who attacked Paris in November.
Brussels has been used a base for Islamic fundamentalism but, until recently, the country was more of a launching pad than a target for homegrown terrorists.
The deadly attacks in Paris in November were conceived and planned by a group based in Brussels, including Abdeslam.
The leader of the cell that attacked the French capital – Abdelhamid Abaaoud – was born in Belgium and the country, a nation of 11 million people, has proportionally more citizens fighting for fundamentalist groups than any other western European country.
Why is there such a strong fundamentalist presence in Belgium?
There are a myriad factors at play. Rising unemployment, disaffected youths and an increase in the migrant population in places such as Molenbeek, a troubled neighbourhood on the fringe of Brussels, attract Isis recruitment teams to such places.
According to the independent International Centre for the Study of Radicalisation and Political Violence, Belgium accounts for 40 fundamentalists per million inhabitants, more than larger countries such as France and the UK.
How many attacks have IS carried out?
CNN states that since June 2014 Islamic State has carried out or been the inspiration for 75 attacks in 20 countries other than Syria or Iraq.
Those attacks, including Tuesday's on Brussels, have killed at least 1280 people and injured more than 1770.
In the past two months there have been at least two other suicide bombings in Europe – one at a Russian police check point in Dagestan that killed two police officers and injured 12, the second was in a busy tourist area of Istanbul that killed four and left 36 injured.
Are there political implications?
Some stocks in Europe tumbled after the attacks at the airport and the metro station while commentators have indicated the fallout could accelerate political momentum among United Kingdom voters ahead of a June referendum.
Voters will decide whether the UK remains part of the European union, or follows the "Brexit" camp and leaves the federation.
Are the attacks revenge for Abdeslam's arrest then?
It is not yet known if the attacks are a revenge attack or had always been planned for March 22.
On Tuesday, Belgium's interior minister said authorities knew that some kind of extremist act was being prepared in Europe but they were surprised by the scale of the attacks in Brussels.
After his arrest on Friday, March 18, Abdeslam's lawyer said he was "co-operating with the authorities" – prompting suggestions that Tuesday's attacks were carried out in revenge for the arrest or by members of a cell that were worried they would be caught if they didn't act.
Professor Dave Sinardet of Vrije Universiteit Brussel told the BBC that it was likely the attacks had been planned for months but were accelerated because of the arrests.
What does it mean for us?
The biggest impact to Kiwis is the potential for more security changes at airports – at the moment most security is at the plane-side part of airports to reduce the risk of airplane bombings and hijackings.
But, the Brussels attacks were carried out in open check-in areas near main doors where there is little security, no baggage scanners and body checks on passengers.
Brussels Airport spokeswoman Florence Muls said European rules do not require closing off those areas and the airport did not have the ability or the mandate to impose controls at the airport terminal entry.
The Independent newspaper states that airports in Istanbul, Nairobi and Bombay already screen passengers and their baggage before they are allowed into the main terminal building because of pervious attacks in those cities.
In New Zealand that could mean moving all check-in counters behind security and those good byes said at the door to the airport, not at the boarding gate.