Operations at a local G4S security firm offices were paralysed on Monday as workers went on strike over alleged harassment by the management.
They also accused the company of slashing their salaries illegally.
The 320 guards claimed a human resources manager who joined the company in December last year, was behind their woes.
Joshua Okoth, who spoke on behalf of the guards, said they received letters last April, indicating that their salaries would be reduced as the company was experiencing financial challenges.
Each guard's pay had reportedly been reduced to Sh14,866 from Sh16,584.
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Okoth said the management did not consult them when it made the decision.
In April, through the Kenya National Private Security Workers Union, the guards went to court, which suspended the decision pending the hearing and determination of the matter.
The union's secretary-general Brian Otiono said: "It has been tough for us. Other than reduction of our salaries, we are being threatened."
He claimed the company had threatened to sack 3,700 guards opposed to the changes.
