Dozens of parents who lost children to the May 12 earthquake kneel outside the courthouse in Dujiangyan, in southwestern China's Sichuan province, Tuesday. (Ng Han Guan/Associated Press)

Chinese police dragged away more than 100 parents Tuesday while they were protesting the deaths of their children in poorly constructed schools that collapsed in last month's earthquake.

The parents, many holding pictures of their dead children, were pulled down the street away from a courthouse in Dujiangyan, a resort city northwest of the Sichuan provincial capital of Chengdu.

"Why?" some of them yelled. "Tell us something," they said as black-suited police wearing riot helmets yanked at them.

The parents had been kneeling in front of the courthouse yelling, "We want to sue." Their children attended a high school in Juyuan, near Dujiangyan, where 270 students died.

Police dragged a reporter and photographers who were covering the protest up the steps into the courthouse, trying to prevent them from seeing the demonstration.

"The parents were here to give their report to the court," said one police officer who refused to give his name.

Chinese police officers take away parents who were demanding the government investigate allegations that some schools, such as the one in which their children died, were poorly constructed. (Ng Han Guan/Associated Press)

Calls to local police were not answered Tuesday.

The protest happened while Chinese leader Li Changchun, the country's fifth-ranked ruler, was touring other parts of the city. Xinhua, the Chinese news agency, said Li was checking heritage sites damaged in the earthquake.

The government says the May 12 earthquake destroyed 7,000 classrooms. Many parents have accused contractors of cutting corners when building the classrooms, resulting in schools that could not withstand the 7.9-magnitude quake. Pictures of collapsed schools surrounded by buildings still standing have fuelled anger.

The Southern Metropolis News quoted a rescuer at the site of the Juyuan school where the 270 students died as saying that rubble from the school showed that no steel reinforcing bars had been used in construction, only iron wire.

The confirmed death toll for China's worst disaster in three decades was raised Tuesday to 69,107, an increase of about 90 people from a day earlier, and 18,230 people are still missing, the State Council said. The quake also left five million people homeless.

Meanwhile, Xinhua said that authorities have delayed for two days an attempt to divert water from a huge lake formed when the quake sent landslides tumbling into a river in Beichuan, in northern Sichuan.

Water levels in the lake had been rising steadily and threatened to flood surrounding areas, prompting authorities to evacuate nearly 200,000 people already uprooted by the quake.

But Xinhua said with little rain forecast for the next several days, rescue workers were not likely to start draining off the water until Thursday. The work had been expected to begin Tuesday.

Workers have already used heavy equipment to dig a runoff channel to remove the water. The government is worried the newly formed lake could burst, sending a wall of water through a valley.

In an indication of how difficult rescue conditions are in parts of Sichuan, there was still no sign of a helicopter that crashed nearly three days ago while ferrying survivors. Thousands of soldiers have been combing remote mountains in search of the military helicopter.

The Russian-designed Mi-171 transport was carrying 19 people, 14 of them people injured in the quake, when it flew into fog and turbulence and crashed Saturday near the epicentre of the quake in the town of Wenchuan, state media reported.