(CNN) Demonstrators across the globe took to the streets on Tuesday to demand better working conditions, as part of rallies marking International Workers' Day.

Held on May 1 each year -- known as May Day -- the rallies date back to the 1880s.

At the time, labor movements around the world were campaigning for safeguards such as eight-hour workdays and trade unions. The date of May 1 was chosen as it coincided with the anniversary of the Haymarket affair in Chicago, where police killed four people at a peaceful protest after someone threw a bomb into the crowd.

Today, trade unions and human rights campaigners continue to mark the day with rallies -- here's a look at this year's protests.

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