Headlines about the award were nowhere to be found in the Chinese-language state media or on the country’s main Internet portals. Broadcasts about Liu Xiaobo (pronounced leo she-ow-bwah) on CNN, which reach only luxury compounds and hotels in China, were blacked out throughout the evening. Many mobile phone users reported not being able to transmit text messages containing his name in Chinese.

But on government-monitored microblogs like Sina.com, which regularly blocks searches for his name, the news still generated nearly 6,000 comments within an hour of the announcement.

The announcement also energized international calls for Mr. Liu’s release, including one from President Obama, who urged China to free him “as soon as possible,” saying that political reforms in China had not kept pace with its economic growth.

Given that he has no access to a telephone, it was unlikely that Mr. Liu would immediately learn of the news, his wife, Liu Xia, said. On Friday night, dozens of foreign reporters gathered outside the couple’s building in Beijing but they were prevented from entering by the police, who posted a sign saying the complex residents “politely refused” to be interviewed. Later, police led away Ms. Liu and her brother, who were told they were being escorted to see Mr. Liu, his brother, Liu Xiaoxuan, said on Saturday. But as of midday, the pair still could not be reached.

Mr. Liu is not expected to accept the prize in person. The award includes a gold medal, a diploma and the equivalent of $1.5 million.

The prize is an enormous psychological boost for China’s beleaguered reform movement and an affirmation of the two decades Mr. Liu has spent advocating peaceful political change in the face of unremitting hostility from the ruling Chinese Communist Party. Blacklisted from academia and barred from publishing in China, Mr. Liu has been harassed and detained repeatedly since 1989, when he stepped into the drama playing out on Tiananmen Square by staging a hunger strike and then negotiating the peaceful retreat of student demonstrators as thousands of soldiers stood by with rifles drawn.