Security personnel on Tuesday clashed with marchers protesting government plans to privatise the ailing national airline, a skirmish that a hospital official said killed at least two protesters and injured eight.
Protesters said paramilitary forces fired after a confrontation as security forces tried to block the strikers nearing the airport in Karachi.
But a spokesman for the paramilitary Rangers force and a senior police officer denied that any of their members had fired.
The violence came as hundreds of airline employees held the latest of a months-long series of protests against the plans to privatise Pakistan International Airlines (PIA).
Police used water cannons and teargas to keep the crowd from approaching the city's Jinnah International Airport before shots were fired.