An Austrian woman is being investigated for the attempted murder and torture of her 12-year-old son after locking him in a small dog cage, authorities said.

The 32-year-old woman is accused of keeping her son in sub-zero temperatures and starving him.

The case has caused outrage in Austria after being made public this week.

The woman has been in pre-trial detention in the town of Krems, north-west of Vienna, since November after a social worker raised the alarm.

The child was found comatose and hypothermic on 22 November after the father - who lives separately - reportedly tipped off authorities.

The malnourished boy had a body temperature of just 26.8C and was close to death after being tortured for months, Johann Baumschlager, police spokesman of Lower Austria province, told the AFP news agency,

The boy was rushed to hospital and his mother was arrested the following day.

The woman is suspected of having doused her son with "cold water several times a day while opening the apartment's windows for several hours amid sub-zero temperatures", Mr Baumschlager said.

The boy has now recovered physically, but "from a psychological point of view, he is still devastated", he added.

The Supreme Court of Justice rejected the woman's complaint against being held in custody for several months in late May.

The investigation is expected to continue until late summer, when a decision over an indictment will be made.