BEIJING - CHINESE police have released five parents of children sickened by melamine-tainted milk, a day after detaining them to prevent them holding a press conference, their lawyer told AFP on Saturday.

The five adults were preparing to speak to the media to demand better treatment for their sick children when they were detained on Thursday evening in Beijing.

'They have all been released,' said lawyer Xu Zhiyong. 'Their (the police's) aim was to stop them from holding a press conference.' Police in Beijing were unavailable for comment.

Mr Ma Hongbin, one of the parents held, refused to talk about his detention, but said his daughter's health was still bad after she drank milk contaminated by the industrial chemical.

'Let's not talk about this, ok?' he told AFP by phone on Saturday of his detention.

He said his 18-month-old daughter had developed kidney stones after consuming tainted milk powder made by Sanlu, one of the Chinese dairy firms at the heart of the scandal.

'She fell ill on Sept 1, and she had very large kidney stones, which have now been evacuated,' Mr Ma said.

'But her situation is still not good, and when the weather changes, you can see her face is a bit bloated. Her fallopian tube has also expanded.'

China's milk scandal came to light in September and has had nationwide repercussions with at least six children dying and nearly 300,000 suffering from kidney and urinary problems after they drank contaminated milk.

Melamine, normally used to make plastic, was added to watered-down milk to make it appear higher in protein.

Journalists were alerted on Wednesday of plans by the parents of affected children to hold a press conference, but the five were held in a centre in the south of the city before being released on Friday evening.

Other worried parents were still able to hold a hastily-arranged briefing on a roadside in the south of Beijing on Friday, and called for urgent research into the long-term effects of the chemical.

One of the mothers told reporters they were not demanding more compensation, but wanted assurance that their children's long-term health would not be affected.

'We are not asking for money, as all the money in the world cannot buy my child's health,' Mr Jiang Yalin, from the south-western province of Guizhou, said on Friday.

The government last week ordered the 22 dairy firms that were found to have sold the tainted milk to pay US$160 million (S$233.9 million) in compensation to the families of babies that died or fell ill. -- AFP