China has dramatically raised the tally of children sickened by dairy products laced with the industrial chemical melamine to 294,000, more than five times the original figure.

In a late-night statement on Monday, the health ministry also said six babies may have died from consuming poisoned milk, up from a previous confirmed death toll of three.

The updated figures showed the problem over contaminated milk in China this year was much greater than the government had acknowledged for months, after it said in late September that just 53,000 babies had fallen ill.

Melamine is a chemical normally used to make plastics, but it emerged in September that it had been routinely mixed into watered-down Chinese milk and dairy products to give the impression of higher protein content.

Melamine can cause kidney stones if taken in excessive levels, and babies who were fed tainted milk powder suffered the worst because they consumed so much of the chemical.

The ministry said the 294,000 children who fell ill had suffered from urinary tract problems and that 51,900 of them had been admitted to hospital for treatment.

A total of 861 children remained in hospital, with 154 of them in a serious condition, according to the ministry.

The central government previously said three babies had died of kidney failure from consuming tainted milk powder, while a regional government also reported one death.

A health ministry spokeswoman confirmed to AFP on Tuesday that the six potential deaths included the three confirmed earlier.