“I am proud to have you as fellow countrymen,” he said.
The PM singled out police, firefighters, paramedics and citizens who stepped forward to help in the aftermath of Friday's attack.
“You can take this pride [in your actions] with you for the rest of your lives,” he said.
Löfven went on to describe the work that he believed necessary to respond to the concern produced by the terror attack, reports news agency TT.
“Friends, this is our fundamental challenge, as social democrats and as Swedes, during this conference and this decade. We are here to respond to this uncertainty,” he said.
Work to combat terrorism must continue across party lines, Löfven continued.
“We will now invite the other parties that passed the national strategy against terrorism so that this work can be continued. We must prevent, obstruct and defend against terrorism with all the resources at our disposal. We will chase these killers with all the strength of our democracy,” he said.
Löfven told TT that he was “frustrated” that the suspected perpetrator of Friday's attack had apparently absconded after having a residency application rejected.
“We need to improve our ability to execute [rulings],” said Löfven, adding that confidence in the system was also a matter of importance.
The second day of the Social Democrat Party conference was opened by foreign minister Margot Wallström, who said that all politics meant “tough trade-offs”.
“Our amendment of migration policy is one of the hardest things I've done as politician,” said Wallström, referring to a tightening of residency laws adopted by the government last year.
Wallström admitted that she had “hesitated for a moment” before committing to the changes.
A common EU asylum system with shared responsibility was the correct way to tackle the issue of migration, she said.
Asylum policy was one of the areas which generated the most debate, reports TT, with several districts, municipalities and representatives motioning for permanent residence to be reintroduced in place of limited terms, as well as more accommodating family reunification rules.
Although migration policy guidelines were not changed during the conference on Saturday, the congress proposed Sunday to adopt the “principle position that permanent residency and the possibility of family reunification increase feelings of security and promote good establishment [in society], reports TT.