Police used tear gas and water cannons to disperse crowds in Athens after the Greek government put forward proposals to make COVID-19 vaccination mandatory in more public-facing roles.
The Greek government has submitted legislation to make inoculation against COVID-19 a pre-requisite for staff at nursing homes and care facilities.
Under the draft bill, staff members could be suspended without pay starting in mid-August if they fail to comply.
The move follows vaccination already being made mandatory for Fire Service personnel, which led to the service transferring non-vaccinated staff to other departments this week.
About 1,500 people gathered in front of the parliament building on Wednesday to demonstrate against the plans.
Participants, many of them unmasked, unfurled a huge Greek flag in the square and some attempted to break through a police cordon, after which officers responded with tear gas and water cannons.
Several thousand also joined a rally in Greece's second-largest city, Thessaloniki. This week's protests followed a similar rally on July 16, which was attended by about 5,000 people.
About 45 per cent of Greece's population has now received two doses of vaccine. Coronavirus infections have been rising in recent weeks, with almost 3,000 new cases recorded on Wednesday.
The government is worried that slow vaccination rates will further harm the economy after a sharp recession last year.