A Brazilian woman and her two adult children, all suffering from dehydration and malnutrition, were freed by police following 17 years of captivity by her husband, authorities have said.

Police had been alerted to the case in a neighbourhood in the west of Rio de Janeiro by an anonymous tip-off.

"The two youngsters, who are the children of the woman and the suspect, were tied up, soiled and starved," Rio's military police, who arrested the father, said in a statement.

The woman and her children, aged 19 and 22 according to local media, were taken to hospital in a state of "serious dehydration and malnutrition", local emergency services said.

According to the G1 internet news site, the mother told authorities that she and her children would sometimes go three days without food and were regularly the victims of physical and psychological abuse.

Her husband, named as Luiz Antonio Santos Silva, with whom she had been married for 23 years, had told her she would only leave his home "when you're dead", she said.

In pictures published by Brazilian media, the adult children looked like adolescents due to their malnutrition.

"When we saw the state of the two children, we thought they wouldn't have survived another week," one unnamed inhabitant of the Guaratiba neighbourhood, where the family lived, told G1.

"I tried to speak to the mother in the ambulance but she was so weak that she didn't manage to make a sound."