A man with blood stains on his sweater leaves Brussels airport in Zaventem on March 22, 2016 following twin blasts. A string of explosions rocked Brussels airport and a city metro station, killing at least 21 people in apparently coordinated attacks, officials said. (DIRK WAEM/AFP/Getty Images) A man with blood stains on his sweater leaves Brussels airport in Zaventem on March 22, 2016 following twin blasts. A string of explosions rocked Brussels airport and a city metro station, killing at least 21 people in apparently coordinated attacks, officials said. (DIRK WAEM/AFP/Getty Images)

Attackers set off bombs at the airport and on a subway train in Brussels, Belgium, Tuesday morning, killing at least 34 people and injuring more than 100, the Associated Press reports.

A news agency affiliated with the Islamic State issued a statement, obtained by The New York Times, claiming responsibility for the attacks:"Islamic State fighters carried out a series of bombings with explosive belts and devices on Tuesday, targeting an airport and a central metro station in the center of the Belgian capital Brussels, a country participating in the coalition against the Islamic State. Islamic State fighters opened fire inside the Zaventem airport, before several of them detonated their explosive belts, as a martyrdom bomber detonated his explosive belt in the Maalbeek metro station."

Two bombs, at least one of which is suspected to have been set off by a suicide bomber, rocked Brussels' Zaventem airport during the morning rush hour. Belgian Health Minister Maggie de Block said that 11 people were killed and 81 were injured at the airport.

An hour later, an explosion on a subway train near the European Union's headquarters killed 20 and injured more than 100 people.

European officials had been bracing for a terror attack for weeks, and those fears were heightened after the capture of a suspect in November's attacks in Paris on Friday. Some officials are calling the attacks an act of war.

"We are at war," French Prime Minister Manuel Valls told reporters after a crisis meeting called by the French president. "We have been subjected for the last few months in Europe to acts of war."

President Obama, speaking from Havana, said, "I want to comment on the terrorist attacks that have taken place in Brussels. The thoughts and prayers of the American people are with the people of Belgium and we stand in solidarity with them.

"The world must unite. We must be together, regardless of nationality, or race or faith, in fighting against the scourge of terrorism," he added. "We can and we will defeat those who threaten the safety and security of people around the world."

Watch more: