Two homemade bombs ripped through cafeterias at China's two most famous universities at lunchtime today, leaving nine injured and shattering a long-held sense that campus life in this country is immune from violent attack.

Fashioned from what police called "homemade charcoal gunpowder," the first bomb exploded at 11:55 a.m. during the lunch rush at Tsinghua University, sometimes referred to as China's MIT. Flying glass injured five professors and a student. About 90 minutes later, a second blast blew out dining hall windows and a door at Beijing University, known as China's Harvard, injuring three.

China's state-run media issued brief reports on the explosions. Hundreds of policemen descended on the leafy campuses, cordoning off the sites and forbidding Chinese journalists to provide information to foreign media outlets.

Police fanned out across the city tonight, stopping cars at random and checking identification. No group immediately asserted responsibility for the bombings, which came a day after a visit to Beijing by Secretary of State Colin L. Powell and a week before China's legislature opens its annual session.

Chinese sources said police in the capital would be under intense pressure to break the case. A failure to solve the crime, one source said, would reflect badly on Hu Jintao, the recently appointed Communist Party chief.

In conversations and in Internet chat rooms, some students quickly fixed the blame on what they called "terrorists." "My friends are afraid of a madman here," said Zhang Wen, a sophomore in Beijing University's English department, speaking from her dormitory room. "There is much panic."

Specifically, Zhang and others said, there was speculation that separatists among the Uighurs, a Turkic ethnic group that inhabits the northwestern province of Xinjiang, could be responsible. Uighur separatists have conducted a sometimes violent campaign in Xinjiang against Chinese rule.

Uighurs were held responsible in March 1997 when a bomb ripped through a crowded Beijing bus. Two people were reportedly killed and 30 injured in that attack.

Because of China's strict laws, guns are hard to obtain, but the raw materials for making bombs are readily available. Fireworks are abundant in China, sold for burials, weddings and other events, and there are commercial explosives used in mining and construction. In the past few years, bombs have been employed as weapons in marital tiffs, business quarrels and extortion rackets, and by laid-off workers committing suicide.

One of the deadliest bomb attacks in China occurred in March 2001 in Shijiazhuang, capital of the northern province of Hebei. That blast, which killed more than 100 people, was set off by a man exacting revenge against neighbors.

The campuses of the two elite schools have been placid since 1989, when students at both were at the center of protests ultimately crushed by the army. These days students seem to have put aside politics, focusing instead on obtaining their degrees and participating in China's economic juggernaut.

Today's attacks shocked and appalled students on the two campuses. "It makes me very angry," said Guo Xin, a freshman studying foreign literature at Beijing University. "Why choose a university?"

At Tsinghua, Cindy Ke, a graduate student in law, said the attacks changed the way she viewed the school. "I have never thought the terrorism would be so near to me. I've never heard about an explosion happening on campus," Ke said. "I am frightened. At dinner, I grabbed my food at the No. 14 dining hall and hurried back to my dorm to eat. I used to eat in the dining hall, but, you know, it's kind of dangerous now."