Police said section 144 of CrPc has been invoked in and around the Sterlite unit to provide security to it as per the orders of the Madras High Court.
However, angered over not being allowed to take out a rally, the slogan-shouting protesters forcibly tried to push back the security personnel in riot gear.
They then started hurling stones at police and also overturned a vehicle after which the security personnel lobbed teargas shells to disperse them, they said.
While more than 20 people suffered minor injuries in stone-pelting incident, some vehicles were set on fire, leading to tension in the area, they added.
Meanwhile, a peaceful demonstration was held near the old bus stand in the town, also demanding the closure of the Sterlite unit and the proposed expansion of the plant.
The district has been witnessing several protests by locals and others against the Sterlite Copper plant here and its proposed expansion.
Protesters have alleged that the plant was polluting ground water in their area.
Sterlite Copper represents the copper unit of Vedanta Limited which operates a 400,000 tonnes per annum-plant in Tuticorin.
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