Following a call from the landlord at 10am yesterday, Hua Mark police rushed to Ritthirat Apartment on Soi Ramkhamhaeng 30, to find German student Ronny Ulbrich, 25, with serious head injuries, lying naked in a poll of blood in his sixth-floor rented room. Near his body, police found a bloodstained dumbbell.

Lt-Colonel Sompop Tunpolngam said police suspected that Ulbrich - who had been enrolled in the open university's international programme - was killed by a blow to the head on Wednesday night following a fight with a male acquaintance.

Police also found bloodstains on a doorknob in another room on the same floor and would soon interview the tenant, the officer said.

Neighbours told police that Ulbrich lived by himself but had male friends coming over to his place almost every night. Earlier yesterday, someone knocked on his door but no one answered. As there was a sign of intrusion, they alerted the landlord who discovered Ulbrich's body.