GSEE and ADEDY, Greece's two largest umbrella unions representing private and public sector workers, gathered for an anti-austerity rally at downtown Kotzia Square on Tuesday at 10 a.m., with plans to march to Parliament later in the day.

The KKE communist party, meanwhile, and its union offshoot PAME, gathered at the Hellenic Steel plant in Elefsina, where workers have been on strike for more than six months. The rally closed off a section of the Athens-Corinth national highway, while Greek Communist Party chief Aleka Papariga was expected to hold a campaign speech at the site.

Seamen have also called a strike, meaning that ferries will be tied up in the port of Piraeus until Wednesday morning.

In Athens, workers at the Piraeus-Kifissia electrical railway (ISAP) and the Athens metro began May Day with a three-hour work stoppage from the start of their shift until 8 a.m., with the latter pulling the brakes on all routes to Athens International Airport throughout the day.

Buses and trolley buses in the Greek capital will begin pulling off work from 9 p.m. on Tuesday as they hold a two-hour stoppage from 10 p.m. until the end of the shift, while the Proastiakos suburban railway and the OSE train will be on strike all day.

Thessaloniki public transport was also facing disruptions as bus drivers walked off the job, while protesters gathered at central Aristotelous Square.