Police in the central Norwegian town leapt into action when they received a despairing telephone call at 5.30am from a man in his twenties in dire need of assistance, broadcaster NRK reports.
Arriving in the city centre, police quickly arrested the suspected assailant before finding an axe nearby.
All the early signs point to jealousy as the driving force behind the actions of the attacker, who is being held in custody as he awaits questioning later on Tuesday.
Although they had broken up and no longer shared a bedroom, the suspect still lived in the same apartment as his former girlfriend, NRK reports.
On Monday night, the woman returned from a night out with another man in tow.
Enraged by the noises he could hear emanating from the room next door, the suspect grabbed an axe, barged in on the pair, and struck the victim on the arm and thigh with the blunt end of the weapon.
Fearing for his life, the young man told police he ran naked from the apartment with his aggressor hot on his heels.
Fleeing down Kjøpmannsgata in the centre of the city, the unclad victim managed to borrow a phone from a passer-by and alert the authorities to his perilous situation.