Thousands of terrified villagers were sheltering in tents in this mountainous corner of southwestern China on Sunday night as rescue workers struggled to distribute supplies to thousands more cut off by a powerful earthquake that Chinese authorities said killed 186 people and injured more than 11,000 others.

At least 21 more people were missing, the authorities said, following the tremor that struck Sichuan province on Saturday morning, not far from the epicenter of a 2008 quake that killed more than 80,000 people and raised questions among many Chinese about their government's ability to respond to crisis, and about the poor quality of construction in many school buildings that collapsed.

tremor：震颤，振动   

Chinese authorities, responding to their first natural disaster since a Communist Party leadership change last year, appear to be moving faster this time to reach stricken areas in the aftermath of Saturday's tremor, which was measured by China's earthquake administration at magnitude 7.0 and by the U.S. Geological Survey at 6.6.

State media said 18,000 military and armed-police personnel had been sent to help with recovery efforts, along with 23 helicopters. In another apparent indication of the Chinese leadership's concern to appear responsive, China's new premier, Li Keqiang, made a high-profile visit to the disaster area before returning to Beijing on Sunday.

But as aftershocks continued to shake the area late on Sunday, blocked and damaged roads meant that rescue workers were still unable to distribute basic supplies in some of the worst affected areas, where residents were sleeping outside without power and water and with dwindling supplies of food, according to residents and state media reports.

dwindling：减少，缩小　　　　

One of the hardest hit areas was Baoxing county, where almost all buildings had collapsed, including many that were built after the 2008 earthquake, according to the state-run Xinhua news agency. It said the death toll in Baoxing alone was 26, with about 2,500 injured, but rescuers were still trying to reach the area on foot to distribute tents and other basic supplies.

One Baoxing resident and local official, Tian Renxian, told The Wall Street Journal by telephone that 20 people in the county were still missing, and most of its 58,000 residents were living in the open air or in tents they had built themselves.

'All the roads are collapsed,' said Ms. Tian. 'Stones are falling down from the mountains so it's very dangerous coming here! There's an aftershock even now while I'm talking to you!'

Xinhua reported that an excavator fell off a 300-meter cliff on the way to Baoxing on Sunday morning, but the number of casualties from that accident were still unknown. Xinhua also said that more than 870 firefighters have been sent to Baoxing with light rescue equipment and 11 sniffer dogs.

xcavator：挖掘机　　　　sniffer：嗅探器

In Longmen village, which state media named as the epicenter of the quake, dozens of houses had been destroyed─mostly older structures made of brick and wood─but by Sunday afternoon any casualties had already been removed from the scene.

Most residents who were unhurt were staying either in a large tent camp on a football field at a local high school, or in tents at a 400-year-old temple that appeared to have survived the quake intact.

In the town of Lushan, seat of the county government, the damage was less widespread, and streets were filled with excavators and vehicles carrying paramilitary police to help with the rescue efforts. But many residents there were also sleeping in tents because their homes had been severely damaged, and with aftershocks still shaking the area, they were unwilling to risk going back indoors.

'Look at the condition of my house,' said Lin Feng, a 45-year-old Lushan resident, pointing to her heavily damaged home. 'I don't think I could just go back and live there with the frequent aftershocks. Even when there is no earthquake, it's impossible for me to live in a room with so many cracks on the wall and one side of the ceiling dropped.'

'I'm not sure how long the tent life is going to last,' she said. 'We are totally lost now.'

Her neighbor, a 34-year-old man who wouldn't give his name, pointed to the damage his own house had sustained, including cracks of five to 10 centimeters in width. 'Yes, it is not completely crushed, but how dare we go back and live there again?' he said.

On the approach to Lushan, some residents stood with cardboard signs asking for water.

Earlier in the day, Premier Li had visited a hospital treating many of the injured and promised them that the government would take care of their medical expenses, according to state media reports. He made the promise while visiting the Huaxi Hospital in Chengdu, the provincial capital, which received 160 seriously injured from the quake area on Saturday night, nine of whom were in intensive care, according to Caijing Magazine.

China's Foreign Ministry thanked foreign governments for offers of help, but said the country was able to cope.