BRUSSELS, March 22 (UPI) -- Belgian authorities continue to search for anyone who planned or participated in the coordinated terror attacks in Brussels that killed at least 34 people and wounded dozens more, officials said late Tuesday.
Three explosions rocked the Belgian capital between 8 and 9 a.m. Tuesday -- two at Zaventem International Airport and one at a nearby metro train station.
Earlier, officials said 20 were killed in the metro blast and 11 at the airport. One official raised the toll by three Tuesday evening, saying the updated numbers would be formally announced early Wednesday.
More than 200 people were injured in the attacks and officials said they expect the death toll to continue to rise. The city's transport system was shut down and the airport will reopen Wednesday.
The Islamic State claimed responsibility for the attacks, but no arrests have yet been reported.
"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," the Islamist group said through an affiliated news agency, The New York Times reported. "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."
The threat level in Belgium was increased to the highest degree after the attacks. Two nuclear power plants in the country were cleared of non-essential personnel for unspecified reasons.
Belgium's Crisis Center said the Belgian Army neutralized a third bomb that failed to detonate at the airport hours after the initial attacks took place.
Some news reports indicated that gunshots were fired and shouts in Arabic were heard before the explosions.
Police released a surveillance image of three men suspected of being behind the attacks. Officials are seeking to identify a man seen in the far right of the image, seen wearing a hat and a white or beige jacket.
"For the time being, I can only confirm that this is a picture of three suspects," Belgian federal prosecutor's office spokesman Eric Van der Sijpt said Tuesday.
"We were fearing terrorist attacks, and now this has happened," Belgian Prime Minister Charles Michel said in an address. "There are many dead and injured."
Michel said the attacks were "blind, violent and cowardly" and a "tragic moment in our country's history," while he called on "everyone to show calmness and solidarity."
Belgian Federal Prosecutor Frederic Van Leeuw previously said the three Brussels-area explosions were terrorist attacks likely carried out by at least one suicide bomber -- before the Islamic State claimed responsibility.
U.S. President Barack Obama commented on the Brussels attacks during his two-day trip to Cuba.
"The thoughts and the prayers of the American people are with the people of Belgium. We stand in solidarity with them in condemning these outrageous attacks against innocent people. We will do whatever is necessary to support our friend and ally, Belgium, in bringing to justice those who are responsible," Obama said Tuesday. "This is yet another reminder that the world must unite. We must be together, regardless of nationality, or race, or faith in fighting against the scourge of terrorism. We can and we will defeat those who threaten the safety and security of people all around the world."
The attacks come four days after Salah Abdeslam was arrested following a large-scale counter-terrorism raid in Brussels. Abdeslam is accused of being an Islamic State militant who helped carry out the Nov. 13 attacks in Paris that killed at least 130 people. It's unclear if Tuesday's attacks are related to Abdeslam's arrest.
France has increased security following Tuesdays explosions and French President Francois Hollande held an emergency Cabinet meeting to discuss the attacks. The Netherlands and Britain have also increased security measures.
After Abdeslam's arrest, police launched a manhunt for Najim Laachraou as police said his DNA was found in safe houses used by Abdeslam. Laachraou is accused of being one of at least three people who taught Abdelslam and sheltered him while he was sought by police in what has been called Europe's largest manhunt.
Brussels is the de facto capital of the European Union, where many E.U. institutions are located. E.U. operations in the city are canceled for Monday.
"I am appalled by the bombings this morning at Zaventem airport and the European district in Brussels which have cost several innocent lives and injured many others. I extend my sincerest sympathies to the relatives and friends of the victims. These attacks mark another low by the terrorists in the service of hatred and violence," European Union President Donald Tusk said in a statement.
"The European institutions are hosted in Brussels thanks to the generosity of Belgium's government and its people. The European Union returns this solidarity now and will fulfill its role to help Brussels, Belgium and Europe as a whole counter the terror threat which we are all facing."