Two are dead following the attack at an IKEA store in Vesteras, Sweden, an hour east of Stockholm.
A third was seriously injured, according to Reuters.
"We found a man and a woman who had knife injuries and who later died of their wounds," local police said in a statement. The motive of the attack was unclear.
A 35 year-old man was seriously injured, Swedish television reported.
"He was brought in from the site of the incident with life-threatening injuries," Lena Moren, head duty nurse at Vasteras hospital, told the SVT public broadcaster.
The BBC adds that a man is in police custody, but no motive has been established.
Update: Bloomberg reports that the third victim is in critical condition and undergoing surgery.
