World leaders have expressed their shock at the attacks in Brussels. Here are some of the reactions:
"We are at war. We have been subjected for the last few months in Europe to acts of war." - French Prime Minister Manuel Valls.
"We realise we face a tragic moment. We have to be calm and show solidarity." - Belgian Prime Minister Charles Michel.
"The King and Queen are devastated by the attacks." - statement from Belgium's royal family.
"These attacks mark another low by the terrorists in the service of hatred and violence." - EU Council President Donald Tusk.
"Terrorists struck Brussels but it was Europe that was targeted, and all the world that is concerned."- French President Francois Hollande.
Image 1 of 14 Injured people in the Brussels airport after two explosions were heard 22 March 2016 picture supplied via twitter credit: GIORGI TABAGARI Giorgi Tabag Image 2 of 14 TOPSHOT - A picture shows damage to the facade of Brussels Airport, in Zaventem, on March 2016 after two explosions in the airport. Belgian firefight Image 3 of 14 A scene of carnage inside the dparture hall of Brussels airport after 2 explosions ripped throught he buidling 22 March 2016 picture supplied via twit Image 4 of 14 Damage to a metro station in Brussels 22 March 2016. Three explosions aon the metro system and two at the Brussels airport rocked the city picture sup Image 5 of 14 Passengers leave a train in a tunnel in the Brussels metro after at least three explosions ripped through the metro system in the Belgian Capital 2 E Image 6 of 14 A victim is evacuated on a stretcher by emergency services after a explosion in a main metro station in Brussels on Tuesday, March 22, 2016. Explosion Image 7 of 14 People are evacuated from Brussels airport after explosions rocked the facility in Brussels, Belgium Tuesday March 22, 2016. Explosions rocked the B Image 8 of 14 People react as they walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium Tuesday March 22, 2016. Explosions ro Image 9 of 14 The Schumann metro station in Brussesl is in lock-down after at least threee explosions ripped throught he metro system follwoing two explosions at Br Image 10 of 14 In this image made from video, emergency rescue workers stretcher an unidentified person at the site of an explosion at a metro station in Brussels, B Image 11 of 14 A member of the Belgian Special Forces tands in the departure hall of Brussels airport after two explosions were heard in the building 22 March 2016 p Image 12 of 14 An image posted to Instagram showing blown-out windows at Brussels airport after two explosions were heard at the Belgian capital airport picture supp Image 13 of 14 A picture taken on March 22, 2016 shows the Eiffel Tower in Paris illuminated in colours of the Belgian flag in tribute to the victims of terrorist at Image 14 of 14 A couple watches as the colors of the Belgian flag are projected on to the Brandenburg Gate in Berlin as the German capital shows its solidarity follo
"Terrorists will never win."- Peter Altmaier, chief of staff for German Chancellor Angela Merkel.
"It is with a heavy heart we learned of these ruthless attacks in Brussels ... The world must stand united to defeat terrorism." - Salem Al Meslet, of High Negotiations Committee, a coalition of Syrian opposition groups engaged in peace talks in Geneva.
The attacks "have once again shown terrorism's global face". - Turkish Prime Minister Ahmet Davutoglu.
"It's time for Europe to understand where the genuine threat is coming from and join efforts with Russia." - Prominent Russian lawmaker Alexei Pushkov.