Guardian.co.uk | Robert Tait in Istanbul

A 15-year-old Turkish girl who was arrested at a demonstration in support of a banned Kurdish group has been jailed for nearly eight years after being convicted of "terrorist" offences, including allegedly throwing stones at police.

A 15-year-old Turkish girl who was arrested at a demonstration in support of a banned Kurdish group has been jailed for nearly eight years after being convicted of "terrorist" offences, including allegedly throwing stones at police.

The case comes amid renewed scrutiny of Turkey's human rights record after it was named as the worst violator of the 47 signatory states to the European convention of human rights.

The girl, who has been named only as Berivan, was detained in the south-eastern city of Batman last October at a rally for the banned Kurdistan Workers' Party (PKK), which is regarded by Turkey, the US and EU as a terrorist group.

A court in Diyarbakir found her guilty of "crimes on behalf of an illegal organisation" after prosecutors alleged she had hurled stones and shouted slogans. She was also convicted of attending "meetings and demonstrations in opposition to the law" and "spreading propaganda for an illegal organisation" despite claiming in court that she did not know what the word propaganda means.

In her defence, the girl denied throwing stones or being part of the demonstration but said she had only stopped to watch it out of curiosity, while on her way to visit an aunt. She was arrested after police mistook her for a demonstrator, she said. She had confessed to the crimes only after being beaten in custody.

In an emotional letter published by the Turkish newspaper, Star, the girl said she had been visiting Batman on a ­family holiday and pleaded to be released. "I want to get out of here. I want to be with my ­family. I always cry here. I cannot get used to this," she wrote. "I have been in jail since 9 October. My heart hurts and I miss my family so much."

As she heard her daughter being ­sentenced, Berivan's mother exclaimed in court: "Did she murder? ­­The ­murderers are not sentenced to such a long prison term."

The initial 13-and-a-half-year sentence was later reduced on appeal to seven years and nine months because of her age.

The conviction highlights Turkey's practice of jailing children for terror-related offences under counter-terrorism legislation introduced in 2006. The law allows courts to try juveniles as adults and to jail them for up to 50 years. Recent official figures revealed that there are currently 2,622 minors in Turkish prisons.

Some 737 minors have been charged under the counter-terrorism legislation since its introduction, according to the Diyarbakir Human Rights Association. Out of 267 tried in the city last year, 78 were given extended jail terms. Last November, a prosecutor demanded sentences of 23 years each for six youths, aged 13 and 14, who were charged with throwing stones and Molotov cocktails.

Campaigners say many of those jailed have been wrongly accused and condemn the convictions as a breach Turkey's obligations as a signatory to the UN Convention on the Rights of the Child.

While most of those jailed are boys, an additional building was recently opened at a prison in Diyarbakir to hold girls aged under 18 who are convicted of participating in banned demonstrations.

Last week, Turkey was identified as the worst violator of the European convention on human rights between 1959 and 2009. According to figures released by the European court of human rights, the country accounted for almost 19% of all violations, with 2,295 judgements issued against it. Turkey also had the highest proportion of violations in 2009, making up 347 out of 1,625 negative rulings. The most common violation was the denial of the right to a fair trial. Turkey also had 30 rulings against it following complaints of inhumane or degrading treatment.