A young man posts his photo with a leaflet demanding freedom for Tibet and telling Chinese police, come and get me. Protesters rise up to defend him, and demonstrations break out in two other Tibetan areas of western China to support the same cause.

Each time, police respond with bullets.

The three clashes, all in the past week, killed several Tibetans and injured dozens. They mark an escalation of a protest movement that for months expressed itself mainly through scattered individual self-immolations.

It's the result of growing desperation among Tibetans and a harsh crackdown by security forces that scholars and pro-Tibet activists contend only breeds more rage and despair.

That leaves authorities with the stark choice of either cracking down even harder or meeting Tibetan demands for greater freedom and a return of their Buddhist spiritual leader, the Dalai Lama _ something Beijing has shown zero willingness to do.

"By not responding constructively when it was faced with peaceful one-person protests, the (Communist) party has created the conditions for violent, large-scale protests," said Robbie Barnett, head of modern Tibetan studies at New York's Columbia University.

This is the region's most violent period since 2008, when deadly rioting in Tibet's capital Lhasa spread to Tibetan areas in adjoining provinces. China responded by flooding the area with troops and closing Tibetan regions entirely to foreigners for about a year. Special permission is still required for non-Chinese visitors to Tibet, and the Himalayan region remains closed off entirely for the weeks surrounding the March 14 anniversary of the riots that left 22 people dead.

Video smuggled out by activists shows paramilitary troops equipped with assault rifles and armored cars making pre-dawn arrests. Huge convoys of heavily armored troops are seen driving along mountain roads and monks accused of sedition being frog-marched to waiting trucks.

For the past year, self-immolations have become a striking form of protest in the region. At least 16 monks, nuns and former clergy set themselves on fire after chanting for Tibetan freedom and the return of the Dalai Lama, who fled to India amid an abortive uprising against Chinese rule in 1959.

China, fiercely critical of the Dalai Lama, says Tibet has been under its rule for centuries, but many Tibetans say the region was functionally independent for most of that time.

In a change from the individual protests, several thousand Tibetans marched to government offices Monday in Ganzi prefecture in Sichuan province. Police opened fire into the crowd, killing up to three people, witnesses and activist groups said.

On Tuesday, security forces opened fire on a crowd of protesters in another area of Ganzi, killing two Tibetans and wounding several more, according to the group Free Tibet.

On Thursday in southwestern Sichuan province's Aba prefecture, a youth named Tarpa posted a leaflet saying that self-immolations wouldn't stop until Tibet is free, the London-based International Campaign for Tibet said. He wrote his name on the leaflet and included a photo of himself, saying that Chinese authorities could come and arrest him if they wished, group spokeswoman Kate Saunders said in an email.

Security forces did so about two hours later. Area residents blocked their way, shouting slogans and warning of bigger protests if Tarpa wasn't released, Saunders said. Police then fired into the crowd, killing a a 20-year-old friend of Tarpa's, a student named Urgen, and wounding several others.

The incident, as with most reported clashes in Tibetan areas, could not be independently verified and exact numbers of casualties were unclear because of the heavy security presence and lack of access. The topic is so sensitive that even government-backed scholars claim ignorance of it and refuse to comment.

The government, however, acknowledged Tuesday's unrest, saying that a "mob" charged a police station and injured 14 officers, forcing police to open fire on them. The official Xinhua News Agency said police killed one rioter and injured another.

"The Chinese government will, as always, fight all crimes and be resolute in maintaining social order," Foreign Ministry spokesman Hong Lei said in comments on the incident.

The harsh response points to a deep anxiety about the self-immolations, said Youdon Aukatsang, a New Delhi-based member of the Tibetan parliament-in-exile.

"They're worried that there is an underground movement in Tibet that is coming to the surface," she said.

Tibetan desperation has been fed both by the harsh crackdown _ security agents reportedly outnumber monks in some monasteries _ along with a deep fear that the Dalai Lama, probably the most potent symbol of Tibet's separate identity, will never return.

The 76-year-old Nobel Peace Prize laureate handed his political powers to an elected assembly last year. That was intended to ensure the Tibetan cause would live on after him, but was met with considerable anxiety among many Tibetans who saw it as a sign he was giving up his role as leader of their struggle.

Dibyesh Anand, a Tibet expert at London's University of Westminster, said resistance to Chinese rule is likely to grow more fierce.

"Protests will get more radicalized since the Tibetans in the region see no concession, no offer of compromise, no flexibility coming from the government," he said.