Swedish Police claims to have arrested the driver of the beer delivery truck that rammed into people at Stockholm's Drottninggatan (Queen Street) on Friday.
The accused was arrested "on suspicion of a terrorist crime through murder," Karin Rosander, a communications director at the Swedish Prosecution Authority, told AFP.
One Swedish newspaper, Aftonbladet, reported that the accused is a 39-year-old man of Uzbek origin. They added that he was a supporter of the Islamic State (Daesh) group.
More from IBTimes India: Akshay Kumar gets trolled on Twitter for winning National Award; check hilarious tweets by haters
The accused was arrested on Friday evening after police released images taken from CCTV footage. The suspect was dressed in a hooded jacket. Another man was arrested later for having associations with the Uzbek man.
While the first arrest was done in Marsta, 40km north of Stockholm, the other was at Hjulsta in the north-west of Stockholm.
"We have investigated several people this evening, who we found interesting in one way or another, and recently we arrested someone we are very interested in," said police investigator Jan Evensson, referring to the Marsta arrest.
More from IBTimes India: Nobel laureate Malala Yousafzai chosen as UN Messenger of Peace
At least four people were killed and 15 were injured after the truck crashed into a department store on Friday. The vehicle was hijacked outside a nearby restaurant.
Swedish Prime Minister Stefan Lofven has described it as a terrorist attack, and has asked for tightening of the borders.
"Terrorists want us to be afraid, want us to change our behaviour, want us to not live our lives normally, but that is what we're going to do. So terrorists can never defeat Sweden, never," he said.
More from IBTimes India: Selena Gomez pops up on The Weeknd's Instagram page
Social media comes together to lend support
People took to Twitter to express their solidarity with hashtag #openStockholm to offer a ride, a meal or a place to sleep.
When we ask our friends in Stockholm how they are doing, they all reply: "Busy offering lifts to anyone who needs it" #OpenStockholm— The Stockholm Review (@StockholmReview) April 7, 2017
When Stockholm goes into lockdown the Stockholmers open their homes. All over the city people are offering housing&dinner. #OpenStockholm— Hanna Gerdes (@HannaGerdes) April 7, 2017
What's shocking about #Stockholm is how unshocking it seems. Atrocities in the heart of Europe's capitals, but we've become numbed to them.— Tom Holland (@holland_tom) April 8, 2017