A Belgian soldier participating in a NATO mission in Lithuania died during an exercise on Friday, Belgian officials said late Saturday.

Belgium’s federal public prosecutor has launched an investigation into the incident.

The soldier sustained an injury during a mortar exercise and died in hospital on Saturday, Belgian Defense Minister Theo Francken and Chief of Defense Frederik Vansina confirmed in a joint statement.

Francken said in a post on X that he is “deeply saddened by the tragic accident,” sending “thoughts and solidarity” to the soldier’s friends and colleagues.

Lithuanian President Gitanas Nausėda also offered his condolences in a post, saying Belgian troops serving with NATO in Lithuania “make an invaluable contribution to the security of our nation and the entire Alliance,” adding: “Their dedication and sacrifice will never be forgotten.”

The Belgian national, who was not identified, was part of the Artillery Battalion in Brasschaat. Nearly 200 Belgian soldiers have been deployed to Lithuania since the summer, as part of NATO’s Forward Land Forces mission, a series of multinational battle groups stationed in eight Eastern European countries.

The Belgian federal public prosecutor’s office said it has opened an investigation into the soldier’s death without providing more information on the case, Belga newswire reported. Belgium’s defense ministry has also launched an internal investigation to determine the exact circumstances of the accident.