A man is being held by German police after walking into a petrol station with his wife's severed head in a bag.
The 40-year-old man, of Turkish origin, was covered in blood when he approached the night counter at about 0400 GMT and asked the attendant to call the police.
Hamburg police said officers found the head in a bag on a grass verge and arrested the man, who was in a confused state and admitted killing his wife.
The body of the woman, aged 39, was found in their nearby flat.
Hamburg police spokeswoman Ulrike Sweden said the man seemed "a bit crazy" and may have to see a doctor before charges can be brought.
She said police found a large knife in the flat in Eissendorf, in the south of the city.
"It seems he used the knife to kill his wife and cut off the head," she told the BBC News website.
The couple's two children - girls aged 13 and six - were found in the flat and taken into police care.
"It seems they didn't see the body or what was going on," the spokeswoman said. A motive for the attack is still unclear.
Both the man and his wife were of Turkish origin, with German citizenship.