The detentions came as Beijing stepped up efforts to blame the exiled Tibetan leader, the Dalai Lama, for protests in which nearly 100 Tibetan monks, nuns and lay people have set themselves on fire since 2009.
The harsh measures are a sign new Chinese leaders installed in November is not easing up on Tibet despite the protests and international condemnation.
The protesters are calling for Beijing to allow greater religious freedom and the return from exile of the Dalai Lama, who lives in India.
Communist troops occupied the Himalayan region in 1951. Beijing says it has been part of China for centuries but Tibetans say it was independent for much of that time and want greater autonomy. The Dalai Lama fled the region in 1959 as Chinese troops crushed protests against communist rule.
The latest detentions occurred in an ethnic Tibetan area of Qinghai province, which abuts Tibet, the government's Xinhua News Agency reported late Thursday. It said 12 of those detained were formally arrested but gave no details of the charges.
Beijing has responded to the protests by sending in security forces to seal off areas and prevent information from getting out, arresting protesters' friends and seizing satellite TV dishes. Despite that, the pace of self-immolations accelerated in November as the ruling Communist Party held a pivotal leadership transition.
The government has blamed the burnings on hostile foreign forces that want to separate Tibet from the mainland.
"The Dalai Lama clique masterminded and incited the self-immolations," said Xinhua, citing a police official. "Personal information, such as photos of the victims, were sent overseas to promote the self-immolations."
The burnings have galvanized many Tibetans, who see them as selfless acts of sacrifice, making it hard for authorities to denounce the immolators.
On Thursday, the Voice of America, a U.S. government-financed broadcaster, denied accusations by Chinese state television and a government newspaper that it encouraged the burnings.
The U.S. State Department expressed concern about the "deteriorating human rights situation in Tibetan areas" and the use of criminal laws against people associated with protesters.
"Our concern is that there are deep grievances within the Tibetan population which are not being addressed openly and through dialogue by the Chinese government," said a department spokeswoman, Victoria Nuland.
Nuland said Washington urged Beijing to "engage in a substantive dialogue" with the Dalai Lama.
"We continue to call on Chinese government officials to permit Tibetans to express their grievances freely, publicly and peacefully, without fear of retribution," she said.