A lorry drove into a crowd on a busy shopping street in Sweden’s capital Stockholm on Friday, killing four people and wounding 15, police said.

Prime Minister Stefan Lofven said everything indicated the crash was “a terrorist attack”. “Sweden has been attacked. Everything points to the fact that this is a terrorist attack,” Prime Minister Stefan Lofven told reporters during a visit in western Sweden. He was immediately returning to the capital.

Prime Minister Stefan Lofven has tightened security at the country’s borders in the wake of the attack, which put central Stockholm in lockdown as the main station, metro, central roads and multiple bus lines shut. No specific threat Sweden had already been on a “high risk” alert level before the attack, but Security Services Chief Anders Thornberg said there had been no warning of any specific threat. “We have said that this may happen, but we had no indication that it could be done now,” he explained. Several countries expressed their condolences as news of the massacre broke, with European Commission President Jean-Claude Juncker calling it “an attack against all of us”.