BEIJING, China (CNN) -- At least one monastery remained sealed off by armed troops in the Tibetan capital days after celebrations marking the awarding of the U.S. Congressional Gold Medal to the Dalai Lama, reported a human rights group.
In its report Tuesday, the International Campaign for Tibet, which opposes Chinese rule there, cited local sources and said that troops were surrounding Drepung monastery in Lhasa, with possibly hundreds of monks still inside.
The monastery was sealed off after "police stopped an attempt by monks to peacefully mark the honor to the Dalai Lama last week," ICT reported.
"Another significant monastery in the city, Nechung, is also apparently closed," the ICT added. The group described "a tense atmosphere in Lhasa (that) has been described as similar to 'martial law,' with increased numbers of troops on the streets."
"Tibetan sources report a buildup of armed police in the city, checkpoints on roads out of Lhasa, and an order to Lhasa citizens not to carry out any religious or celebratory activities," the ICT reported.
When asked about the report, a staff member at the Chinese Foreign Ministry spokesperson's office told CNN he was unaware.
There has been no reaction from the Chinese government in its state-run Xinhua news agency.
In a separate report, the Tibet Centre for Human Rights and Democracy, which also opposes Chinese rule in Tibet, said that Chinese authorities arrested eight Tibetans, including a Drepung monk, celebrating the Dalai Lama's honor.
U.S. President George W. Bush bestowed the award -- his nation's highest civilian honor -- on Tenzin Gyatso, the 14th and current Dalai Lama, on October 17 in the Capitol Rotunda.
After the award, China warned that the United States "gravely undermined" relations with China, and it demanded that Washington stop supporting the exiled Tibetan spiritual leader and take steps to repair ties.
Since its 1951 invasion, the People's Republic of China claims to be the rightful and legitimate government of Tibet. However, ongoing sovereignty disputes have called into question the legitimacy of that claim.
The White House has said it believes the Dalai Lama is calling for more autonomy from communist China, including more freedom for Tibetans to practice their religion.
China, however, sees the Dalai Lama's work as part of "separatist activities." E-mail to a friend
All About Tibet
Drepung monastery. 
Armed Chinese police have surrounded and sealed off two monasteries in Tibet after monks began to celebrate the Dalai Lama's honor of receiving the United States Congressional Gold Medal. At least 100 monks are reported to be held inside the Drepung monastery and its not known if any have been injured or arrested. Earlier, at least 3,000 police surrounded the Zhaibung Monastery.

"Chinese police stopped an attempt by monks to peacefully mark the honor to the Dalai Lama last week by sealing off the monastery. Tibetan sources report a buildup of armed police in the city, checkpoints on roads out of Lhasa, and an order to Lhasa citizens not to carry out any religious or celebratory activities," said the International Campaign for Tibet in a report.

Other protesters and monks are reported to have been arrested and injured when police began to clash with the celebrations which started on October 16 inside the monastery. Beginning in the morning on October 17, police began to intervene to stop the celebrations throughout Tibet.

China claims that it is not aware of any report, and has not commented on the situation in Tibet.