Monday's deadly earthquake occurred on a fault where South Asia pushes against the Eurasian landmass, smashing the Sichuan plain into mountains leading to the Tibetan highlands. Worst affected were four counties including the quake's epicenter in Wenchuan, 60 miles northwest of Chengdu. Landslides left roads impassable Tuesday, causing the government to order soldiers into the area on foot, state television said. Heavy rain prevented four military helicopters from landing. In Chengdu, the region's commercial center and the capital of Sichuan province, the airport closed for seven hours, reopening only for emergency and a few outbound flights. A major railway line to the northeast was ruptured, stranding about 10,000 passengers, the state-run Xinhua News Agency said. Although most of the power had been restored by nightfall, phone and Internet service were spotty, and some neighborhoods remained without power and water. Nervous residents spent the night outside, some playing cards or heading to the suburbs. State news media, citing the Sichuan seismology bureau, reported 313 aftershocks. "Traffic jams, no running water, power outs, everyone sitting in the streets, patients evacuated from hospitals sitting outside and waiting," Ronen Medzini, an Israeli student in Chengdu, said via text message. When it hit shortly before 2:30 p.m., the quake rumbled for nearly three minutes, witnesses said, driving people into the streets in panic. "It was scary," said Liu Haiming, who stood amid hundreds of people gathered outside an office tower in eastern Beijing, 900 miles from the epicenter. "We felt the building moving and rushed downstairs even before any announcement." While most buildings in the city held up, those in the countryside tumbled. The city of Mianyang ordered all able-bodied males younger than 50 to take water and tools and walk or drive to Beichuan, where most of the buildings had collapsed. The magnitude-7.9 quake, the biggest to hit China in three decades, killed nearly 10,000 people, Xinhua reported. The earthquake hit one of the last homes of the giant panda at the Wolong Nature Reserve and panda breeding center, in Wenchuan County, which remained out of contact, Xinhua reported. In Chengdu, the quake crashed telephone networks, leaving parts of the city of 10 million in darkness hours later. "We can't get to sleep. We're afraid of the earthquake. We're afraid of all the shaking," said 52-year-old factory worker Huang Ju, who took her ailing, elderly mother out of the Jinjiang District People's Hospital. Wenchuan's Communist Party secretary appealed for air drops of tents, food and medicine. "We also need medical workers to save the injured people here," Xinhua quoted Wang Bin as telling other officials who reached him by phone. The disaster hit less than three months before the Beijing Olympics. International Olympic Committee President Jacques Rogge sent condolences to Chinese President Hu Jintao, adding: "The Olympic Movement is at your side, especially during these difficult moments." Premier Wen Jiabao, a geologist by training, called the quake "a major geological disaster," and traveled to the disaster area to oversee rescue and relief operations. "Hang on a bit longer. The troops are rescuing you," Wen shouted to people buried in the rubble of a hospital. "As long as there's the slightest hope, we should make our effort a hundred times, and we will never relax," he said outside a collapsed high school in Juyuan where at least 50 people were killed and as many as 900 students were trapped in rubble. Contributing: USA TODAY's Calum MacLeod, Associated Press