A religious school teacher was stabbed and slashed by a family member, believed to be mentally unstable, at a double-story house in Setapak here on Monday night.

In the 8.30pm incident, Khariah Hashim, who works at Sekolah Rendah Agama Al Amin here was attacked by the man who was armed with a knife.

The 49-year-old mother of four sustained a stab wound in the abdomen and was also slashed on the forehead.

Wangsa Maju police chief Supt Mohamad Roy Suhaimi Sarif said two of Khariah's sons found her writhing around in agony at the ground floor of the house in Jalan Rejang when they returned from a nearby playground.

He said the victim alleged a 21-year-old relative had stabbed and slashed her.

"Her 14-year-old son claimed to have seen the relative attack his mother. We are in the midst of tracking the alleged assailant who has gone into hiding," he said here on Tuesday.

Mohamad Roy said Khariah was warded at the Kuala Lumpur Hospital. Her condition was described as serious.

He said the police had seized a 45cm-long knife, believed to be the weapon used in the attack, at the scene of the crime.

Mohamad Roy said the alleged assailant's father had told the police that the man was mentally ill and had undergone psychiatric treatment.

"According to the father, the alleged assailant had not taken medication over the past two weeks," he added.