The 40-year-old mother of three was found dead in her Umeå apartment after the blaze was extinguished.
“When we arrived it was a fully developed apartment fire. The emergency team searched through the building and found one person. They revealed later that the person was dead,” explained Håkan Isekling of the Västerbotten police to the TT news agency.
Several people who lived in nearby apartments were taken to hospital with burns and smoke related injuries.
A man, who was also in the apartment block, has been arrested and is being held in custody on suspicion of murder and arson.
According to the Aftonbladet newspaper, the man and the deceased woman were married, although the relationship had already seen trouble before the weekend.
The man had threatened his wife during the summer, leading him to serve four months in psychiatric care, wrote the paper.
On Sunday morning, police stated that the woman had been murdered, although they refused to say more.
“Right now we are not giving out any further details about the suspect, neither the age nor his relation to the woman,” said Peder Jonsson of the Västerbotten police to TT.
The suspect was interrogated on Sunday, as were witnesses and residents of nearby apartments.
The woman’s body has been taken for an autopsy.