Sri Lanka sent hundreds of soldiers to key hospitals to help look after patients on Thursday, as hospital orderlies and administrative staff launched a one-day strike nationwide over allowances.

Sri Lanka is in the midst of its worst financial crisis in over seven decades which has sent the cost of living soaring and forced the government to increase taxes and limit public employees' perks.

"Following a request from hospital directors, 615 soldiers and 19 officers have been deployed at 25 hospitals," military spokesman Major General Rasika Kumara told Reuters.

The soldiers are engaged in non-medical support including offloading ambulances, moving patients and record keeping, he added.

Sri Lanka's once vibrant public healthcare system is struggling as healthcare workers migrate, public healthcare expenditure is trimmed and costs increase.

Sri Lanka's Cabinet approved a monthly transport allowance of 70,000 rupees ($214) for doctors this week, sparking protests from other healthcare workers who responded with the strike.

"Healthcare workers deserve to be treated the same," Ravi Kumudesh, convenor of the Health Services Trade Union Alliance, told reporters.

"The government is giving relief to doctors but leaving out other hospital staff who are also part of giving critical care to patients. That is why they are on strike."

(Reporting by Uditha Jayasinghe; Editing by Nick Macfie)