Hundreds of Muslims have set fire to at least 10 Buddhist temples and 2,100 homes in southern Bangladesh, according to officials.
The violence on Saturday night came in reaction to an allegedly derogatory image of the Quran, the Muslim holy book, posted on Facebook.
"They became unruly and attacked Buddhist houses, torching and damaging their temples from midnight to Sunday morning," Joinul Bari, a government administrator, told the AFP news agency.
"At least 100 houses were damaged. We called in army and border guards to quell the violence," he said, adding that authorities had temporarily banned public gatherings in the area to prevent further clashes.
Nojibul Islam, a police chief in the coastal district of Cox's Bazaar, said at least 20 people were injured in the attacks that followed the posting of a photo of a burned copy of the Quran on the social networking site.
Torching and looting
Protesters blamed the photo on a local Buddhist boy, but it was not immediately clear if the boy actually posted the photo.
Rumia Khatun, a local police officer, said that about "25,000 Muslims chanting God is Great" first attacked a Buddhist hamlet in Ramu, torching centuries-old temples, and later stormed Buddhist villages outside the town.
"I have seen 11 wooden temples, two of them 300 years old, torched by the mob. They looted precious items and Buddha statues from the temples. Shops owned by Buddhists were also looted," said Sunil Barua, a local journalist on the scene.
Bari, the government administrator, said authorities had detained the boy's parents and that an investigation was under way.
Buddhists, who make up less than one per cent of Bangladesh's 153 million population, are based mainly in southeastern districts, close to the border with Buddhist-majority Myanmar.
Although the South Asian country has witnessed deadly clashes between Muslims and Hindus in the past, sectarian
clashes involving Buddhists are rare.
In recent weeks, tens of thousands of Muslims have hit the street across the country to protest an anti-Islam video that mocked the Prophet Mohammed.