Frances Harrison and Elmo Fernando
BBC correspondents in Colombo
The army and air force were deployed to help run hospitals as up to 85,000 Sri Lankan health workers went on strike on Wednesday.
The strike does not include nurses or doctors
The health service trade union alliance, which represents 59 unions, says it wants discrepancies in pay for its members resolved.
The government promised to address health workers' grievances after a previous hospital strike but unions say it has failed to take action within the agreed time.
The Health Service Trades Union Alliance says the indefinite strike is affecting 1,000 hospitals across Sri Lanka.
The strikers are auxiliary staff, not doctors or nurses.
Plans have been put into force to deploy the security forces to help run the major hospitals in the capital and drive ambulances. Leave has been cancelled for health ministry staff.
One children's hospital, two maternity hospitals and a cancer hospital in Colombo have been exempted from the strike and the unions also say they will try to help emergency services keep going in major hospitals.
The workers say they have been asking the government to address their grievances over pay for many years in vain.
They say there are huge anomalies in salaries enjoyed by different workers and they will not end their action until the government takes action.
Speaking before the strike began, Minister of Health, Nutrition and Welfare P Dayaratna said the Treasury had asked for six weeks to decide among the proposals they had presented to solve the situation.
Mr Dayaratna said a huge sum of money was needed and that the unions should consider their responsibility to what he called the poor patients.