A Turkish man has decided to divorce his wife after DNA tests showed he was the father of only one of their twin boys.

The Turkish daily newspaper Sabah reported the security guard from Istanbul, identified only as A.K., had DNA tests done on the three-year-olds after becoming suspicious his wife had been unfaithful.

The tests established with a 99.99 per cent certainty that the man was the father of only one of the boys, adding that the result was confirmed by a forensic medicine institute upon the request of the court handling the divorce case.

The mother, identified as C.K., had maintained a relationship with a lover she had dated before her family forced her to marry A.K., the newspaper said.

The phenomenon of twins with different fathers - known as heteropaternal superfecundation - is very rare in humans but more common in animals such as cats and dogs.

It becomes possible in rare circumstances when a woman produces two ova in a menstrual cycle, said Professor Rusen Aytac, head of the gynaecology department at Ankara University's medical faculty.

A.K. kept the boy he had fathered and disowned the other one, who ended up in a state care institution, Sabah said.

C.K., for her part, has received death threats both from her own and her husband's family, and secured a court order preventing relatives from coming within 500 metres of her, it added.