Explosions hit Brussels’ international airport and a subway station near European Union institutions.

Explosions rocked Brussels’ international airport and a subway station near European Union institutions on Tuesday, killing more than two dozen people and injuring many in what authorities described as terrorist attacks. A suicide bomber was behind at least one blast at the airport and authorities were looking into whether some attackers could be on the run, the Belgian federal prosecutor said at a press conference. The explosions come days after the arrest of Salah Abdeslam, one of the alleged Paris attackers who was captured in Brussels after a four-month manhunt. Security was tightened across Europe, including at Germany’s largest airport in Frankfurt, at U.K. transport hubs and at train stations and airports in France. Belgian officials immediately raised the country’s terror alert to its maximum level and shut the entire public transport system in Brussels and asked people to stay where they were. French President Francois Hollande called the blasts an attack on the whole of Europe and said the continent must take action to better defend itself. “Terrorism has struck Belgium, but it was Europe that was targeted and everyone who is affected,” Mr. Hollande said in Paris. The first two explosions Tuesday morning hit the main airport just outside the city in Zaventem near the check-in counters at about 8 a.m., filling the area with smoke and sending tiles crashing down from the ceiling. Witnesses described blood from the many injured spread across the floor and panic as people rushed to flee. After 9 a.m. local time, another explosion hit at the Maelbeek metro station, near the heart of the European quarter, home to some of the EU’s main institutions. Officials said more than a dozen people were killed at the airport and that at least 15 were killed and 55 wounded at the station. Belgian Federal Prosecutor Frédéric Van Leeuw said it was too early to give a precise number of victims, but some were gravely injured.

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