HAVANA - President Barack Obama on Tuesday called for nations around the world to unite to defeat terrorism, saying the thoughts and prayers of Americans were with Belgium after the attacks in Brussels that killed 34 people."We must be together regardless of nationality or race or faith in fighting against the scourge of terrorism," Obama told Cubans during a historic visit to Havana. "We can and we will defeat those who threaten the safety and security of people all around the world."Earlier Tuesday, a suicide bomber blew himself up at Brussels airport on Tuesday killing at least 14 people and a further blast tore through a rush-hour metro train in the capital shortly afterwards, claiming 20 lives.CNN reported that up to 130 people were also injured in the attacks.A witness said he heard shouts in Arabic shortly before two blasts struck the packed airport departure lounge. Pictures on social media showed smoke rising from the terminal building through shattered windows and passengers fleeing down a slipway, some still hauling their bags.All public transport in Brussels was shut down, as it was in London during 2005 militant attacks on the underground that killed 52. A further 225 soldiers were sent into the city and the Belgian Crisis Centre, clearly wary of a further incident, appealed to the population: "Stay where you are".The blasts at the airport and metro station occurred four days after the arrest in Brussels of a suspected participant in November militant attacks in Paris that killed 130 people. Belgian police had been on alert for any reprisal action.US Secretary of State John Kerry spoke with his Belgian counterpart and they agreed that the attacks on Brussels airport and a metro train on Tuesday "underscored the need for a continued and concerted push by all nations to counter violent extremism." During the phone call, Kerry and Foreign Minister Didier Reynders also agreed to stay in touch as the investigation into the attacks that killed 34 people proceeds, the US State Department said in a statement.