NEW DELHI, May 24 (Xinhua) -- Authorities in southern Indian state of Tamil Nadu Thursday ordered the closure of a major copper smelting plant in the port city of Tuticorin, which was the epicenter of violent protests that led to deaths of 13 people in police firing.

Local police opened fire to control a mob of over 20,000 people who suddenly went on a rampage while staging a anti-pollution protest, demanding the closure of Sterlite Copper, a smelting plant owned by London-listed Vedanta Resources, in Tuticorin Tuesday and Wednesday.

Sterlite Copper's operational license had expired in April and the company was awaiting the state government to renew it. The Tamil Nadu State Pollution Control Board has turned down the licence renewal plea from the company.

The environment regulator's action came after the state high court Wednesday halted the proposed expansion of the company.

The protests against Sterlite Copper have been going on in the city for the past three months, but intensified this week, following media reports that the company owning the copper smelting plant was seeking renewal of its licence for another five years and even planning an expansion.

Though Tamil Nadu's Chief Minister Edappadi K. Palaniswami has ordered a judicial inquiry into the shootings after defending police action, the country's main opposition Congress party has described the deaths as "a brutal example of state-sponsored terrorism."

"These citizens were murdered for protesting against injustice," Congress leader Rahul Gandhi said.

The state's main opposition DMK party has also slammed the government for failing to address the concerns of the local people.

"The plant should be shut down," state opposition leader M.K. Stalin had said as he compared the police firing on protestors to a British-era crackdown on Indians in the northern state of Punjab's Jalianwala Bagh.

Some five years back, hundreds of people had to be hospitalized after they complained of breathlessness and nausea, following a gas leak from the plant. Locals claim the plant has been polluting groundwater in the area.

Vedanta has, however, denied all the allegations against it and said it plans to double the capacity of its plant.

"We do have all the required permissions on ground to proceed with our expansion project," Vivek Thomas, a spokesperson for Vedanta, told the media.