Chinese authorities were stepping up efforts to ensure drinking water and sanitation for the tens of thousands of people living without basic necessities since Monday's earthquake.

"We are sending 48 movable water-purifying machines to quake-hit areas, as airdropped bottled water is far from sufficient," Minister of Housing and Urban-Rural Development Jiang Weixin said Friday.

Two machines had already arrived in Chengdu and another six were expected to reach the Sichuan provincial capital on Friday night, he added.

Each machine could purify 30 to 50 tons of slightly polluted water, making a potable supply for 5,000 to 10,000 people every day, said Li Dongxu, head of the ministry's urban construction department.

In Sichuan alone, water supply facilities were severely damaged in about 20 cities and counties, and the situation was thought to be more serious in many other counties and townships, according to preliminary assessments.

The water supply networks in Chengdu, Mianyang and Guangyuan had been repaired for household supply, but supply was disrupted in Dujiangyan and Mianzhu as water pipes were damaged and could not be replaced quickly, though water plants were still working, according to Li.

However, people in hard-hit counties like Beichuan and Wenchuan were surviving on airdropped bottled water alone, as water supply facilities were destroyed, Li added.

The ministry was also shipping 800,000 water purification tablets to the quake zone, and 500,000 tablets arrived in Chengdu on Thursday morning.

A thousand household water purification sets were also arranged, with 700 to arrive at Chengdu on Saturday.

 "The quake-hit areas are in urgent need of portable toilets," Jiang said. Conditions in the temporary accommodation areas were becoming inconvenient and insanitary.

Forty portable toilets were available in Beijing, Shanghai, and Chongqing to be transported to Sichuan, and 10 were en route, Jiang said.

The ministry also planned to send 3,000 portable gas burners to quake areas, so that people could cook, instead of living on biscuits and instant noodles, Jiang said.

He said the ministry was working on plans for temporary housing, as permanent homes would take time to build.

"It's possible that we could build in the near future some houses where people could live for two or three years, but some people would rather accept subsidies and look for housing from their relatives and friends," Jiang said.

The ministry would send experts to Sichuan to study proposals, and the final plan would be subject to the approval of the State Council, he said.

A 45-strong panel of building safety experts were also sent into quake areas to inspect homes that suffered minor damage, he said. Residents were still afraid of staying inside their own homes even if there were only some small cracks in the walls.

"People could move indoors again once some houses were proved to be safe, and this would bring some relief to survivors."

Damage to buildings in the quake-hit areas was extensive, said Jiang, who had just returned from Sichuan Province.

More than 4 million apartments and homes had been damaged or destroyed in Sichuan, Jiang said, citing provincial government figures from two days ago.