MADRID (AFP) - A Spanish mother accused with her ex-husband of drugging and suffocating their adopted Chinese daughter denied they gave the child sedatives, in a tearful first testimony at their trial on Thursday.

Rosario Porto, a former lawyer, and her former husband, journalist Alfonso Basterra, are accused of murdering 12-year-old Asunta Yong Fang Basterra Porto, whom they adopted when she was a baby.

They have both denied the charges.

Dressed all in black, Porto, 46, bowed her head and wept as she gave her first testimony at the trial in the northwestern city of Santiago de Compostela.

Prosecutors questioned Porto about her divorce from Basterra and Asunta's wellbeing in the months leading up to her death in September 2013, when the child's body was found in a wood near the city.

The couple are accused of drugging Asunta with the sedative Orfidal periodically for three months and finally asphyxiating her, according to court documents.

In extracts of the hearing broadcast on television, Porto said she last saw her daughter on the pavement outside their house in Santiago after she dropped Asunta off there on Sept 21.

In a summary judgement released in late 2013, the judge said Porto had given conflicting accounts of Asunta's disappearance and had asserted that Basterra had given the girl "white powder".

In Thursday's hearing, Porto told the court that nobody to her knowledge had given Orfidal to the girl.

At the time of Asunta's death, the couple were separated but say they were raising their adopted daughter together.

"As a couple we did not do very well. But I think that as parents we did the best we could," Porto told the court.

Asked whether she had been concerned for Asunta's welfare, Porto replied in a tearful voice: "That was my only concern."

She also told the court, however, that she had been suffering from depression that year and had herself been taking the sedative Orfidal.

"When you are depressed you can scarcely look after yourself," she said.

DRUGGED AND SUFFOCATED

The case shocked Spain and drew international attention when it came to light, prompting a statement of concern by the Chinese foreign ministry.

Porto was questioned on Thursday about her movements around her country home near where Asunta's body was found.

Basterra, 51, was due to testify later in the day or on Friday.

The judge wrote in a summary in 2013 that Basterra was suspected of having "administered to the child a toxic dose of Orfidal to deprive her of all will and defence and presumably to ease the action of asphyxiation, in a plan agreed with Rosario".

Spanish media in the courtroom on Thursday reported that Porto burst into tears when prosecutors showed her photographs of Asunta's corpse.

Lawyers in the case could not immediately be contacted to comment on the hearing.

The prosecution has demanded the couple receive prison sentences of up to 20 years.

The court has called scores of witnesses and experts to testify. Trial hearings are scheduled to run until Oct 21.