The woman, Olga Borisov, and her husband Ilan Yehuda, of Rishon leZion, have both been arrested.

A woman from Rishon Lezion allegedly murdered her four-year-old son by drowning him in the waters of the Mediterranean Sea near the town of Bat Yam.

During a remand hearing, Yehuda cried out: "My son is dead, how can I stay under arrest? It's over. I'm through."

Though the judge said that the father did not appear to have been involved in the murder, he ruled that releasing him from custody could jeopardise the investigation and remanded him for three days.

The mother's lawyer said that her client was mentally unstable. She had killed the child, who suffered from development issues, because she thought "it would be a solution to his problems".

The lawyer said that Borisov had intended to commit suicide immediately afterwards, but was unable to do so.

In a note found in her purse, she had asked for her husband's forgiveness. "I love the child, but I don't want to die with him," she wrote.

The family had emigrated from Russia in 1992.

The woman's husband was being questioned in an attempt to find out whether he was aware of the fact that the child was in danger.

According to the father, he returned home at 11 pm and did not find his wife and son, leading him to believe that they had gone to a friend. When they failed to return, he called the police. Then police received at a call at 1.30am from people on the beach who reported seeing a woman throwing a boy into the water.

According to Israel Radio, the bystanders tried in vain to save the boy by pulling him out of the water and performing mouth-to-mouth resuscitation.

ZAKA volunteer Shlomi Katz said: "My hands are still shaking from the thought that a four-year-old child was proclaimed dead."