Stockholm - Proceedings opened Wednesday in a Swedish court against a German woman suspected of beating two young children to death and injuring their mother.

Prosecutor Frieda Gummesson said the woman had used a hammer or similar tool to repeatedly hit the children, aged one and three, and their mother, who survived the attack with injuries.

The motive for the March 17 attack in the small town of Arboga appeared to be that the German woman refused to accept her former partner had begun a new relationship with the mother of the children, the prosecutor said.

The student, who denies the charges, was dressed in a blue shirt. In addition to her Swedish lawyer, Per-Ingvar Ekblad, the 32-year-old woman is accompanied by her German lawyer.

An interpreter was also available but the woman appeared to be able to follow the proceedings held in Swedish.

The woman was extradited to Sweden at the end of April and has since been held in Vasteras, 100 kilometres west of Stockholm.

The slain children's parents as well the mother's new partner on Wednesday demanded damages from the German woman. The mother, who is due to testify during the trial, still suffers from impaired vision and hearing.

The trial is held at the district court in Koping, near Vasteras.

Gummesson will summon 56 witnesses including a psychiatrist, suggesting that the trial could last three weeks.

Police have not found the instrument and there was also no DNA evidence linking the woman to the scene, but the prosecutor has said she was confident in gaining a conviction.

In addition to witnesses there was forensic evidence including shoe prints and surveillance camera footage from Arboga railway station and Skavsta airport, south of Stockholm.

The German woman said she went to Arboga to visit the site of an ancient runestone.

Other evidence included lists of telephone calls, e-mails and notes from the German woman's computer as well as a map of the neighbourhood that was found in her possession. (dpa)