According to the preliminary investigations, a woman born in 1930 had been in the laundry room of an apartment building on Monday afternoon in Oulu, northern Finland.
Around the same time, a man entered the room, and by threatening the elderly woman with a sharp-edged weapon he conducted sexual violence to her.
The elderly woman had told about the incident to her relatives and they had called the emergency number.
Several police patrols arrived at the scene along with the paramedics.
The woman was taken to the hospital.
After the incident, the police soon caught a man, 22, near the crime scene.
The man is suspected of aggravated rape.
On Thursday afternoon, the man was imprisoned in the Oulu District Court. The arraignment was conducted with the aid of a live video stream from the police prison at Haukiputaa, in North Ostrobothnia.