The former boss of the dairy firm at the heart of China's tainted milk scandal stood trial here Wednesday over a trail of death and sickness that pushed Chinese products off shelves worldwide.

A small but vocal group of protesters gathered outside the court in this northern Chinese city, calling for justice after milk laced with an industrial chemical killed six babies and left 294,000 with kidney and urinary problems.

"They should execute them all," shouted Hua Lian, a 45-year-old woman who described herself as a milk consumer, as roughly half-a-dozen relatives of sick children held up signs calling for justice.

"They have to deal with these people harshly. Otherwise people will never learn."

But lawyers monitoring the case for the families said the legal process had been flawed and that there was little chance of justice for the victims.

The former head of the Sanlu Group, Tian Wenhua, and three colleagues were put on trial on charges of producing and selling defective products, which lawyers said would mean a maximum punishment of life in prison.

The charges were weaker than lawyers for victims' families had initially expected, extinguishing the possibility that the four would face the death penalty.

Tian's lawyer, Liu Xinwei, told AFP during an afternoon recess that Tian had not yet entered a plea.

The official Xinhua news agency said the trial ended without an immediate verdict just after 10:00 pm (1400 GMT). The report said the verdict "will be announced at an unspecified future date" without giving further details.

Sanlu was the first and biggest dairy producer found to have this year sold milk laced with melamine, a chemical used to make plastics which was mixed into watered-down milk to give the appearance of higher levels of protein.

In all, 22 Chinese dairy firms were found to have sold tainted milk, and the government last week ordered them to pay 160 million dollars in compensation to the families of babies that died or fell ill.

However the families and their lawyers criticised the sum as woefully inadequate, with some parents set to only receive about 300 dollars.

"I'm a farmer. I don't have money to pay for the treatment. My son is still sick and he's not been able to get treatment," said one man who demonstrated outside the court before police pushed them away.

The protesting relatives held up sheets of paper that read: "The victims have a right to participate in judicial proceedings."

This reflected an apparently widespread complaint from the victims' relatives that they had not been allowed to tell the courts their version of events, and that authorities had rejected civil compensation lawsuits.

"We asked to participate in the trial, in the prosecution. We felt that we had a right to participate as we represent the victims," said Xu Zhiyong, a lawyer working for a group of people seeking to sue Sanlu and other milk firms.

"But the court refused to allow us. They didn't want the testimony of the people we represent. We think the court has violated legal procedures."

Foreign press were not allowed inside the Shijiazhuang court, but Chinese state-run television and news services were let in to publicise the case.

In China, trials are often held behind closed doors and last just one day.

China's careful efforts to publicise the trials appeared to reflect the government's intent to show domestic and international audiences it was taking the issue seriously.

The milk scandal became a global problem after it emerged some of the tainted products had been exported, leading to recalls of Chinese dairy foods around the world.

It was just the latest in a spate of Chinese made products to have been recalled from overseas in recent years due to safety concerns, with other problem products including toys covered with lead paint and deadly pet food.

The four Sanlu executives are the highest profile figures to be hauled before the courts over the scandal, after 17 people mostly accused of being middlemen went on trial in recent days.

Those verdicts have yet to be announced but some of the defendants could face the death penalty.