Lt-Col Andre Traut said a 28-year-old man died and five other people were injured in the same protest.
“This matter is now the subject of an investigation conducted by the Independent Police Investigative Directorate (IPID) and police will not be in a position to divulge the finer details of the case.
“The man died as a result of police action, but we cannot give more details of the incident.”
IPID spokesman Moses Dlamini said an investigator was on his way to the scene to get more details.
“I can confirm that one person was killed. However we only have a report that three were injured. An investigator is on his way to gather more details.”
Democratic Alliance spokesman Zak Mbhele said unconfirmed reports received by the party also indicated that a farmer had been killed in the province.
“Another unconfirmed report is that a farmer was attacked by a mob of protesters and beaten to death. We have no further details at this stage.”
Traut said police were trying to find out about the second killing.
Grape harvesters in the Hex River Valley have been protesting for over a week about their wages, demanding R150 a day. Most earn between R69 and R75 a day, with R80 being the highest and only offer from farmers so far.
Protesters have been blocking roads and burning tyres across the province.
“The widespread unrest by farmworkers... is a matter of concern and although every endeavour is made to maintain law and order, it is fair to admit that our response time is compromised and affected by the situation,” Traut said.
AfriForum called on President Jacob Zuma and Police Minister Nathi Mthethwa to intervene.
“We expect minister Mthethwa to personally visit the scene and to ensure that the transgressors are prosecuted successfully,” deputy CEO Ernst Roets said in a statement.