At least 21 people were killed and many more injured after terrorist bomb attacks on the main airport and the Metro system in Brussels.

The coordinated attacks came as the Belgian capital was on a high level of alert following the arrest of Paris atrocity suspect Salah Abdeslam in the city last week.

There were unconfirmed reports of shots being fired and shouting in Arabic at the airport in what Belgian media said was a suicide attack.

At least one explosion hit the Metro system near a station close to European Union buildings.

On the Metro, traveller Evan Lamos tweeted a picture and video of passengers climbing from his train into the tunnel, saying: "We are being evacuated from the back of the Metro, between Schuman and Maelbeek.

"Smoke in the tunnel as we evacuate."

The picture was reminiscent of images after the July 7 attacks in London.

Images on social media showed the injured being treated in the street.

As well as the airport, the whole Metro system was closed.

The first news of the attack came when the airport was rocked by a double blast with reports of up to 10 dead and many more injured.

Jef Versele, 40, from Ghent, Belgium, was at the airport when he heard the two explosions.

"I was on my way to check in and two bombs went off - two explosions," he said.

"I didn't see anything. Everything was coming down. Glassware. It was chaos it was unbelievable. It was the worst thing."

He added: "People were running away, there were lots of people on the ground. A lot of people are injured."

Mr Versele was two or three storeys above the source of the explosion but he said many people around him were hurt.

"The bomb was coming from downstairs. It was going up through the roof. It was big.

"About 15 windows were just blown out from the entrance hall", he added.

The explosion was close to the American Airlines desk.

Images on social media showed shattered windows and smoke rising from an airport building.

People could be seen fleeing in terror in video footage shot from an airport car park.

Footage from inside the building showed a scene of devastation with ceiling tiles strewn across the floor and suitcases abandoned.

Passengers were led onto the tarmac and travellers were urged to stay away from the airport.

Brussels Airport, which handles serving 23.5 million passengers per year, told users on Twitter: "There have been two explosions at the airport. Building is being evacuated. Don't come to the airport area.

"Don't come to the airport - airport is being evacuated. Avoid the airport area. Flights have been cancelled.

"All airport operations have been suspended until further notice. Follow the information on our website.

"Passengers that are still located in other areas in the airport are asked to remain calm and wait for further information."

Prime Minister David Cameron called a meeting of the Government's Cobra emergency committee and tweeted a message of support, saying: "I am shocked and concerned by the events in Brussels. We will do everything we can to help."

Greater Manchester Police said they have also increased patrols.

Assistant Chief Constable John O’Hare said: “First and foremost, our thoughts are with all those who have been affected by the incidents in Brussels today.

“There is no specific threat in Greater Manchester following the events this morning but we remain at a threat level of severe.

“We are working closely with Manchester Airport to ensure that the appropriate response is in place and we have increased our patrols to support this.

“We will continue to review the situation and maintain our increased patrols in crowded areas, iconic locations and transport hubs.

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“The events today in Brussels reinforce the need for us all to remain vigilant and report any concerns whilst continuing with normal daily life.”

Chief Constable Ian Hopkins said: “My heartfelt condolences go out to all of those affected by the shocking terrorist attacks in Brussels this morning.  Whilst there is no specific threat to our communities here in Greater Manchester, it is a reminder to us all of the need to be vigilant. I would urge people to report anything suspicious to the Police.

"Officers and staff from Greater Manchester Police and the North West Counter Terrorism Unit work tirelessly to keep us all safe, but we can only do this with the continued support of the public.

"The aim of terrorists is to divide society and spread fear. At this awful time our communities across Greater Manchester should stand together and support each other more than ever. We will stand be standing together with them."

UKIP Deputy Leader Paul Nuttall spoke of his outrage over the explosions at Brussels Zaventem airport.

He said: “This is an appalling attack, killing and maiming innocent people just going about their business.

"My heart goes out to the victims and their families and I hope that those involved, directly and indirectly, in causing this horrendous incident are quickly brought to justice.

“These incidents highlight the dangerous times in which we live but we must not be cowed down by these attacks on our society,” said Mr Nuttall, North West MEP speaking from the European Parliament building in Brussels.

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Yasmin Qureshi, MP for Bolton South-East, wrote on Facebook: “Very worrying news unfolding in Brussels. Thoughts with emergency services and all those affected.”

The Metro explosion killed 15 and injured 55, 10 critically, transport operator STIB told Belgian broadcaster RTBF.

French Prime Minister Manuel Valls, quoted by broadcaster France Info, said: "We face a particularly elevated threat. We are at war. In Europe we have been subjected to acts of war for several months."

At a press conference Mr Michel called the attacks "blind, violent and cowardly".

He added: "We must face this challenge in solidarity, united, together."

All flights between the UK and the main airport in Brussels have been cancelled for the rest of today after attacks in the Belgian capital.

Brussels Airport announced that it will be closed until Wednesday following two explosions in the departure hall.

Brussels Airlines cancelled 25 flights between UK airports - Heathrow, Manchester, Birmingham, Bristol and Edinburgh - and Brussels.

All Eurostar trains to and from Brussels were suspended, with services from London terminating in the French city of Lille.

Security has also been stepped up at transport hubs in the UK.

The Foreign and Commonwealth Office (FCO) updated its travel advice for Britons in Brussels, urging them to "stay away from crowded places and avoid public transport at this time".

British officials in the city have been given the same instructions, the FCO said.

A spokesman for travel organisation Abta said British holidaymakers in Brussels should follow the instructions of the Belgian authorities, while those due to travel should contact their transport provider.

He added that although Belgium is a popular destination for UK visitors, March is "one of the quieter months for leisure travel".

Are you in Brussels or affected by the attacks? Contact us via webdesk@nqnw.co.uk