One man has been sentenced to death and 28 others jailed for their roles in a slave labour scandal at brick factories in northern China.

The foreman of a kiln where more than 30 people were held captive was jailed for life, and an employee received the death penalty for killing a worker.

Others were jailed on charges of illegal detention and forced labour.

Since the scandal broke in June, more than 570 people forced into slavery in Shanxi and Henan have been freed.

The case has drawn widespread anger and unusually strong criticism from the state-run media.

It emerged after some 400 distraught parents of children who had been sold into slavery set up an online campaign to raise awareness of the issue.

Officials punished

Judge Liu Jimin of the Shanxi People's High Court announced the verdicts in a televised ruling.

"The black brick kiln incident is an ugly social phenomenon and an ulcer on socialist China... we must get rid of it," he said.

The factories were reportedly run like prisons, with workers - some of them children - facing beatings from guards and injury from long working hours.

The kiln where the accused foreman, Heng Tinghan, and his employee, Zhao Tanbing, worked was owned by Wang Bingbing, the son of a local Communist Party official, who was jailed for nine years.

On Monday, 95 officials in Shanxi province were punished for dereliction of duty in supervising the brick kilns, state media reported.

Thirty-three were sacked from their posts and another 62 were given disciplinary warnings, Xinhua news agency said.

There are expected to be more trials connected with the scandal. Police in northern China have arrested almost 160 people suspected of involvement in the case.