Sweden’s prime minister has warned that his country is facing the biggest threat in its modern history after a gunman in Brussels killed two Swedes in an attack that authorities are investigating as terrorism.

“Sweden has in modern times never been under as big a threat as now,” Ulf Kristersson told reporters on Tuesday.

Kristersson said Sweden and the European Union needed to bolster their borders and internal security to prevent dangerous individuals from staying in the bloc.

“Every indication is that this is a terror attack, targeting Sweden and Swedish citizens, just because they are Swedes,” he said, adding that the region “can’t be naive.”

Two Swedes were shot dead in Brussels and another was wounded on Monday night as Belgium hosted Sweden in a Euro 2024 qualifying football match.