Beijing - China's top leaders have urged officials across the country to respond to the growing scandal over tainted milk after one government department said it had received more than 100,000 complaints about dairy products, state media said on Sunday.

The government has ordered a complete overhaul of the dairy industry after tainted milk powder killed at least four infants and sickened some 6,200 others.

Vice Premier Li Keqiang on Saturday visited a hospital treating babies stricken by melamine-laced milk powder in the northern province of Hebei, where many of the cases of melamine-related illness were recorded.

Li also talked to doctors at Hebei's Dingxing county hospital and met dairy farmers and staff at a local supermarket, the government's Xinhua news agency said.

At a meeting of government ministers and top leaders of the ruling Communist Party on Friday, President Hu Jintao criticized some local officials for their "perfunctory work style, lax management and lack of responsibility".

"Some officials have ignored public opinion and turned a blind eye to people's hardships, and even major issues that concern the lives of the masses of people," the official China Daily quoted Hu as saying at the meeting.

"We must learn a painful lesson from the recent accidents," the newspaper quoted him as saying, adding that he was apparently referring to the milk scandal and recent mining disasters.

Hu said that such problems meant that the Communist Party "faces an unprecedented heavy task in building itself."

The World Health Organization (WHO) expressed satisfaction on Sunday with the response of the Chinese government in containing the spread of the tainted infant milk

The State Administration for Industry and Commerce on Saturday launched a nationwide inspection of all dairy producers, wholsalers and retailers.

The administration issued an urgent circular ordering local officials to verify the qualifications of all dairy businesses and ensure that unlicensed ones were closed down.

It had received 106,143 complaints and refunded the cost of 304.38 tons of dairy products by Saturday morning, the newspaper said.

The government leaders demanded "all-out efforts" to save infants sickened by consuming tainted baby milk powder, the agency said.

Three leading dairy producers - Yili, Mengniu and Bright Dairy - were stripped of the government's "famous brand" label on Friday after melamine was found in some of their products.

Health inspectors on Friday said they found melamine in some liquid milk and yoghurt sold by each of the three companies.

Melamine is used as a binding agent and coating for particle, fibre and laminated board in furniture. It is also used to make fertilizer.

Hebei police have formally charged 18 people who sold melamine to milk producers or sold contaminated milk, and detained at least a dozen other milk dealers, melamine traders, company officials and local quality supervisors.

Hebei is the home base of Sanlu, which supplies nearly a fifth of China's market with an inexpensive baby formula implicated in many of the 6,200 reported cases of melamine-related illness.

Government officials said Sanlu knew about the contamination of milk powder with melamine since March but didn't order a national recall of the powder until last week.

Apart from the four infants who died, at least 158 babies had developed serious kidney problems, reports said. (dpa)