"We shall continue to respond firmly, calmly and with dignity when faced with a threat. We shall remain confident. Our strength lies in this confidence," the king said in a televised message.
"[Queen] Mathilde and I share your pain, the pain of those who lost their loved ones and who suffered in this cowardly and horrible act of terrorism. We express our support for the rescue and security services members, we express our appreciation to those who offered their help spontaneously," King Philippe stressed.
Earlier in the day, a series of blasts hit Brussels' Zaventem airport and a central metro station, killing at least 34 people and injuring up to 250 others. The Belgian authorities are treating the explosions as part of a coordinated terrorist attack.