It has been alleged that the clash was triggered by firing by a private security belonging to the contractor.
Additional District Magistrate Vivek Chandel confirmed the death of three labourers who were identified them as Harry, Tej Singh and Simarjit, all hailing from Fatehpur in Punjab. However, sources put the number of deaths at four.
He said that further details about the incident are awaited as senior officers of police and administration were still at the spot.
"The union leaders were having some dispute over wages with contractors executing work at north campus of IIT but firing by private security of the contractor vitiated the atmosphere, leading to clashes," said president of state unit of CITU Kashmir Singh.
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The union members were trying to persuade the labours of the contractor to join the stir when they were allegedly fired at leading to the clashes.
The enraged Union members attacked the labour of the contractor and chased them. Two persons died on the spot while two other succumbed to their injuries on way to the hospital, sources said.
The labour Union members, joined by some local people, went on rampage and set three vehicles on fire.