Armed British police officers stand on duty in front of the Elzabeth Tower better known as 'Big Ben' outside the vehicle entrance to the Houses of...
{"Image ImageDescription": "Armed British police officers stand on duty in front of the Elzabeth Tower, better known as \"Big Ben\", outside the vehicle entrance to the Houses of Parliament in central London on March 22, 2016.\nBritish Prime Minister David Cameron tweeted that his country would do \"everything we can to help,\" and announced that Britain's COBRA security committee would meet Tuesday. COBRA meetings are held to discuss how the government responds to emergency situations and bring together ministers, police and intelligence officers. A string of explosions rocked Brussels airport and a city metro station on Tuesday, killing at least 21 people, according to firefighters, as Belgium raised its terror threat to the maximum level.\n / AFP / ADRIAN DENNIS        (Photo credit should read ADRIAN DENNIS/AFP via Getty Images)"}