China vowed to defend its sovereignty in Tibet as Chinese troops set up checkpoints and mobilized to quell an uprising. A deadline for protesters in the Tibetan capital to turn themselves in passed without any apparent surrenders or arrests.

In the central government's first comment on the anti-China protests in Tibet, Foreign Ministry spokesman Liu Jianchao blamed the violence in Lhasa on supporters of the Dalai Lama, the revered spiritual leader who fled in 1959 after a failed uprising against Chinese rule.

"The Chinese government will unwaveringly protect its national sovereignty and territorial integrity," ministry spokesman Liu Jianchao said at a hastily called news conference Monday. "The violent acts have demonstrated the true nature of the Dalai clique."

Some residents reported Monday that Lhasa had quieted down and many people were returning to work. Chinese military police reportedly set up many checkpoints to control movement.

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"All across the city today there are checkpoints where you can only enter if you have a permit," said Marion Berjeret, an intern for a French fashion design company who has lived in Lhasa for four months.

She said foreigners have been moved to the outskirts of the city, where the situation was less tense.

Police were doing "door-to-door searches and just going in and ripping apart and looking for insurgents" as of Sunday, said Susan Wetmore, a Canadian who arrived by plane Monday in Chengdu in neighboring Sichuan province.

In Beijing, Liu accused the Dalai Lama's supporters of being behind sometimes violent demonstrations at Chinese embassies and consulates in the U.S., Europe and Asia.

German police detained 25 Tibetans on Monday after demonstrators tried to force their way into the Chinese consulate in Munich and spray-painted "Save Tibet" and "Stop Killing" on the building. Tibetan protesters also clashed with police in Nepal and India.

Protests inside China have spilled from Tibet into neighboring provinces and even the capital, Beijing, where students staged a vigil Monday. There were reports of Tibetans clashing with police Monday in regions near Tibet.

The upheaval is prompting scrutiny of the communist government's human rights record ahead of the Aug. 8-24 Beijing Summer Olympics, which China had hoped would boost its international image.

"This is a China engaged with the world which is using the Olympics to demonstrate a new openness, and it risks all of that collapsing in on it if it is seen as being the enforcer of a crackdown on Tibetans," said Mark Malloch-Brown, the British Cabinet minister in charge of Asia relations.

But Liu said the violence would not hurt the Olympics.

"I think they made the wrong calculation of their situation," he said of the protesters. "We will continue our great efforts in making the Olympic Games a great success."

U.N. Secretary-General Ban Ki-moon on Monday urged Chinese authorities to exercise "restraint" in Tibet — his strongest message on the violence to date.

"I'm increasingly concerned about the tensions and reports of violence and loss of life in Tibet and elsewhere," he told reporters outside the council's chambers.

Asked whether he sees a U.N. role toward Tibet, Ban answered: "We will continuously monitor the situation; we'll get back to you."

In Washington, Secretary of State Condoleezza Rice said Beijing should find a way to work with the Dalai Lama, who she said is not a separatist and could "lend his moral weight" to bringing stability to Tibet.

The Tibetan protests began March 10 on the anniversary of the failed 1959 uprising. Tibet had been effectively independent for decades before Chinese communist troops entered in 1950.

Champa Phuntsok, Tibet's China-appointed governor, said Monday that the death toll from the unrest had risen to 16 and that dozens were injured. He denied a claim by the Dalai Lama's government-in-exile in India that 80 Tibetans were killed during the protests in Lhasa.

As the streets of Tibet's capital swarmed with troops, Champa Phuntsok denounced the protesters as criminals and vowed severe punishment if they did not surrender by midnight Monday.

"If these people turn themselves in, they will be treated with leniency within the framework of the law," he told reporters. Otherwise, he added, "we will deal with them harshly."

No arrests or surrenders were reported by the deadline. A woman who answered the telephone at the Lhasa Public Security Bureau after midnight refused to answer questions.

China restricts access by foreign journalists to Tibet, and officials kicked out the few in the region, making it difficult to verify information about the protests, the biggest and fiercest in almost two decades.