Outrage swelled Wednesday over the deaths of 10 protesters at a rally over a copper plant in southern India, after police opened fire on demonstrators in what critics termed "mass murder".
Violence erupted Tuesday in Tamil Nadu state at a long-running demonstration demanding the closure of the smelting plant owned by British mining giant Vedanta Resources which residents say is causing environmental damage.
The state's chief minister has ordered a judicial inquiry into the shootings but the move failed to stem rising anger over the clashes, which also left about 80 wounded.
M.K. Stalin, leader of the main Tamil Nadu opposition party the DMK, said police were guilty of "atrocities".
"Mass Murder of Innocent People," he tweeted Wednesday. "Who ordered the police firing on protestors? Why were automatic weapons used to disperse the crowd and under what law is this permitted?"
A video of a police officer on top of a bus and pointing an assault rifle at crowds has fuelled fresh anger.
Rahul Gandhi, the national leader of the opposition Congress party, has called the deaths "a brutal example of state-sponsored terrorism".
"These citizens were murdered for protesting against injustice," he said.
Police said Tuesday that 12 people had died but later revised the toll in the port city of Tuticorin.
P. Mahendran, superintendent of Tuticorin district police, said 18 officers were also wounded in the clashes.
"The situation is tense but under control today," he said. "The post mortem on the bodies is being conducted and they will be handed over to families today."
The plant, about 600 kilometres (375 miles) south of Tamil Nadu's state capital Chennai, is currently closed as Vedanta's Sterlite Copper subsidiary seeks a new licence so it can be expanded.
- 'Unavoidable circumstances'-
The protesters had set ablaze the local administrator's office after they were denied permission to hold a rally at the plant.
Police said efforts to disperse the crowd of several thousand with a baton charge and tear gas volleys failed before authorities used live ammunition.
Tamil Nadu chief minister Edappadi K. Palaniswami ordered the judicial inquiry into the shootings but defended the police.
"The police had to take action under unavoidable circumstances to protect public life and property as the protesters resorted to repeated violence," he said.
The families of each victim would be offered one million rupees ($14,700) compensation, he added.
The deaths came on the 100th day of demonstrations against the plant, which environmentalists and residents claim is contaminating water sources -- a charge the company denies.
The protests intensified after Vedanta, owned by an Indian billionaire but with its head office in London, sought to double the 400,000-tonne annual capacity of the plant.
It was shut briefly after an alleged gas leak in March 2013 that left hundreds with breathing difficulties, nausea and throat infections.
The company maintains that it adheres to environmental standards and said it was the victim of "false propaganda" about its operations.
Tamil Nadu is one of India's most industrialised and prosperous states and similar protests over environmental concerns have turned deadly in the past.
Tuticorin witnessed violent demonstrations in 2012 over a nuclear power plant in neighbouring Kudankulam district that left one person dead.