Hundreds of people were injured, including at least three Finns.
Responding to the explosions that struck Brussels airport and its metro system, Finnish President Sauli Niinistö issued a statement of condolence on Tuesday.
"The attacks in Brussels are a continuum of the attacks in Paris, as well as of other terrorist acts such as the suicide attack in Istanbul last Saturday, and the terror [that] Isil is spreading in Syria and Iraq," the statement said. "Finland unequivocally condemns all forms of terrorism. On behalf of the people of Finland, I express my deepest sympathy for the families of the victims and for the people of Belgium."
Prime Minister Juha Sipilä took to the microblogging site Twitter to express his concern.
"The news about the explosions in Brussels is shocking. A strike at the heart of the EU affects us all. My sincere condolences to the friends and family of the victims," Sipilä wrote.
A short while before Sipilä, Finance Minister Alexander Stubb also tweeted a comment on the incident.
"Shocked to hear about the explosions at Brussels Airport. Condolences to the victims and their families," Stubb posted in English.
The first blasts occurred shortly after 8am local time (10am Finnish time) at the capital's Zaventem Airport. About an hour later another blast went off at Maelbeek metro station, which lies close to EU buildings.
On Tuesday afternoon, Belgian public broadcaster VRT raised the death toll from the twin attacks, with 20 people killed in the blast on a metro train and 14 in explosions at the airport. Dozens are also injured.
Federal officials in Brussels have since confirmed that the airport explosion was caused by a suicide attack. Meanwhile other local officials were urging commuters to stay put as public transportation in the city had come to a standstill. The airport was also shut down following the attack.
Edit: 2:25 pm Niinistö comment added; number of fatalities updated.