School support workers are also taking to picket lines in a protest about pay.
The latest industrial action comes as legislation is to be debated which could lead to the restoration of the Northern Ireland Assembly and Executive in the coming days.
The UK government has committed funding to cover public sector pay deals if Stormont returns but unions have not called off the strike.
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Traffic chaos on the Cregagh road during this mornings rush hour into the city. Photo: pacemaker
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