At the centre of the strike is a dispute between nurses and midwives with the latter staging a strike protesting authorities' decision to train nurses in midwifery, Xinhua reported.
President of the Government Midwifery Service Association (GMSA) Devika Kodithuwakku told reporters that nurses were trying to drive midwives out of maternity wards by taking over their duties.
The midwives are accusing the nurses of attempting to coerce them into caring for people over 65 years with a special nurses training course. Nurses in Sri Lanka used to be trained only to assist midwives in labour rooms.
Health workers have threatened a continuous strike if issues not resolved
"Our service has been in place since the 1880s and we are not going to let this travesty happen," Kodithuwakku said.
As many as 30,000 health workers from 38 trade unions around the country are estimated to have joined the protest, according to union officials. A group also protested outside the health ministry on the outskirts of Colombo.
Heavy traffic was visible in key areas of the city as hundreds of protesters marched for a long list of demands from the government including better pay and work conditions.
The health workers have threatened a continuous strike if their issues are not resolved.