Eight left-wing protesters were shot dead by Indian police during a demonstration in the southern state of Andhra Pradesh, officials have said.
At least sixteen people were wounded in the incident
Police had been pelted with stones as they approached a tent where communist supporters were gathered, and responded by opening fire, said a state minister.
Saturday's protest was called as part of a three-month campaign demanding land for the poor.
Opposition parties called a strike in response to the shooting.
The leader of the opposition TDP, N Chandrababu Naidu, said Andhra Pradesh Chief Minister Y S Rajasekhara Reddy "has no right to continue in office after innocent people have lost their life".
Mr Reddy ordered a judicial inquiry and said: "I will not comment on who is responsible unless we get the full report."
Sixteen people were reported to have been injured in the shooting, which took place in Mudigonda, a small village in the southern state.