Four people were killed and nine injured in Himachal Pradesh when two factions of workers, involved in the IIT-Mandi construction work near here, clashed with one another, police said.
One of the two groups wanted members of the other to abstain from work to support their call for a strike over some demands, which led to the clash. Three vehicles were also torched.
"Two labourers died on the spot, while two succumbed to injuries in a hospital," Superintendent of Police Mohit Chawla told IANS. He said the injured were hospitalised.
"The striking workers forced the employees of the other contractor to abstain from work. This led to tension between the two groups, resulting in firing by private security guards of the contractor, whose employees were on the job," said Chawla.
In retaliation, a mob attacked the security guards and the employees, which led to the deaths of four people.
Two were lynched by the mob comprising around 250 people carrying 'lathis' and stones, while the other two reportedly died after falling down from a steep hill, said another police official.
Three people also suffered bullet injuries.
The IIT campus is located in Kamand village near here, some 175 km from the state capital Shimla.
Director General of Police Sanjay Kumar told reporters in Shimla that the incident was related to a clash among workers of two contractors - one supporting the strike and the other refusing to join in.
CITU general secretary Kashmir Singh Thakur told reporters that the striking workers were indiscriminately fired upon by five to six hired gunmen of the contractor.
He said the workers were on strike to press their demands, including release of salary.
Thakur alleged the gunmen were hired by contractor Rajiv Sharma.
Centre of Indian Trade Unions (CITU) is affiliated to the Communist Party of India-Marxist.
However, no IIT official was available for comment.