Bangladesh police on Tuesday charged thousands of villagers with vandalism and assault after demonstrations against a Chinese-backed power plant in which four protesters were shot and killed by police.

Dozens more protesters were wounded when police opened fire on Monday in the village of Gandamara on the southeastern coast where twin power plants are to be built in a $2.4 billion project backed by two Chinese companies.

The villagers say their protests were peaceful but police say 11 officers were hurt, including one who was shot in the head. They have arrested at least three villagers over the violence.

"We've filed cases against around 3,200 people for the violence. We've identified 57 of them but the rest are unnamed," local police chief Swapan Kumar told AFP.

Kumar said local people oppose the power plants because they fear the resulting pollution would damage the environment and force them from their homes.

The villagers had been holding peaceful protests for days after S. Alam Group, the Bangladeshi conglomerate behind the project, began levelling farmland in preparation for building the plants.

They fear the case registered by police could give authorities extra powers to harass or detain anyone protesting against the project.

"Police will now use their power indiscriminately against any villager who speaks against the plants," a schoolteacher who lives in the village told AFP by phone on condition of anonymity.

Hundreds of villagers staged further protests against the plant on Tuesday, demanding justice for the four victims.

Local media reports say the group plans to build two coal-fired power plants on the site on the edge of the Bay of Bengal, with the capacity to produce 1,224 megawatts.

The two Chinese firms -- SEPCOIII Electric Power and HTG -- are financing $1.75 billion of the plants' estimated $2.4 billion cost, the Daily Star newspaper said.

Authorities in Chittagong district, where the site is located, have ordered an investigation into the clashes.

They come after thousands of people demonstrated last month against plans to build massive coal-fired power plants on the edge of the Sundarbans, the world's largest mangrove forest.

Experts say the plants would cause major damage to the delicate ecosystem of the area, home to endangered Bengal tigers and Ganges dolphins.