The man turned himself in to police at around 2.30am and the woman was later found in an apartment in the Stockholm suburb.
“It’s a relationship matter,” said Marie-Louise Nilsson, Stockholm police spokesman.
A murder investigation has begun but according to Nilsson it’s still unclear how police will eventually classify the crime.
“It could just as well be manslaughter or assault,” she said.
The man is being held in custody in Södertörn police station. By 7am on Thursday he had not been questioned and the prosecutor had not made a decision about how to proceed with the case.