A protester was killed by a rubber bullet in southern India Wednesday, a day after 10 were shot dead when police opened fire on a rally demanding the closure of a copper plant, officials said.
Tuesday's police firing, which also left about 80 people injured, sparked intense criticism. Amnesty International said police had "many questions to answer" and those responsible should be brought to justice.
On Wednesday police fired rubber bullets at the crowd and sent volleys of live ammunition overhead, officials and witnesses said, after protesters in the port city of Tuticorin hurled home-made bombs and pelted them with stones.
"We fired live ammunition in the air to disperse the protesters. But the mob continued to pelt stones and bombs. They were setting fire to vehicles," a police officer told AFP.
"We were forced to fire rubber bullets which unfortunately hit one man in the spine and he died," he added. Another police officer at the scene also said a 22-year-old man had died.
A video on social media Wednesday showing a police officer atop a bus pointing an assault rifle at the crowds has fuelled fresh anger.
The demonstrators are demanding the closure of a copper plant on the outskirts of Tuticorin in the southern state of Tamil Nadu owned by British-based mining giant Vedanta Resources, which they say is causing environmental damage.
Witnesses said demonstrators set fire to a police bus Wednesday and ransacked a liquor shop. TV footage showed police in riot gear patrolling streets littered with stones and burnt tyres.
Traders shut down shops as authorities imposed a curfew in parts of the city.
Tamil Nadu chief minister Edappadi K. Palaniswami ordered a judicial inquiry into Tuesday's shootings but defended the police response.
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 protesters? Why were automatic weapons used to disperse the crowd and under what law is this permitted?"
Rahul Gandhi, the national leader of the opposition Congress party, on Tuesday described the deaths as "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. P. Mahendran, superintendent of Tuticorin district police, said 18 officers were wounded in the clashes.
The Madras Union of Journalists complained of police heavy-handedness. "A group of policemen and rogue elements snatched and damaged the cameras," said journalist S. Raghunathan.
The plant is currently closed as Vedanta's Sterlite Copper subsidiary seeks a new licence so it can be expanded.
The deaths came on the 100th day of demonstrations against the plant, which environmentalists and residents say is contaminating water sources -- a charge the company denies.
The protests intensified after Vedanta, owned by Indian billionaire Anil Agarwal 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 states and similar protests over environmental concerns have turned deadly in the past, including in Tuticorin.
Vedanta's share price closed at 250 rupees ($3.65) after losing more than seven percent on the Bombay Stock Exchange. The stock had opened at 263 rupees per share.