PHOTO: KIRO
Now playing
02:46
Violent May Day clashes rock Seattle
Paris May Day demo Jim Bitterman lklv_00004503.jpg
Paris May Day demo Jim Bitterman lklv_00004503.jpg
Now playing
00:54
Clashes in Paris over proposed labor bill
Now playing
01:56
Revolutionary May Day celebration in Cuba
dnt wa may day protests police injured_00004313.jpg
PHOTO: KIRO
dnt wa may day protests police injured_00004313.jpg
Now playing
01:07
3 officers injured during May Day march
lok watson turkey may day demonstrations_00000000.jpg
lok watson turkey may day demonstrations_00000000.jpg
Now playing
02:13
Turkish forces clash with protesters
pkg damon ukraine donetsk may day clashes_00003920.jpg
PHOTO: Reuters
pkg damon ukraine donetsk may day clashes_00003920.jpg
Now playing
01:53
Police and protesters clash on May Day
pkg chance russia moscow may day _00004004.jpg
pkg chance russia moscow may day _00004004.jpg
Now playing
01:39
Russians use May Day to support Putin

Story highlights

Nine people were arrested

Five officers were injured

May Day protests in Seattle have been marred by violence in recent years

(CNN) —  

May Day protests in Seattle turned violent on Sunday, as protesters lit fireworks and threw rocks and Molotov cocktails at police, Seattle Police said.

After a peaceful march was held earlier in the day, nine people were arrested and five officers were injured in the clashes, according to police.

Seattle Mayor Ed Murray thanked police for their “extraordinary work” in a statement.

“It is unfortunate and deeply regrettable that in a city that goes to incredible lengths to respect First Amendment rights, there are some who disregard our values and engage in senseless acts of violence and property destruction,” he said. “My thoughts are with the officers who were injured.”

One officer sustained a facial laceration, another was bitten and a third was hit by a Molotov cocktail but not burned.

Seattle Police Chief Kathleen O’Toole said that her officers underwent “enhanced crowd management training” and had planned for the May Day unrest.

What is May Day, anyway?

The city is known for having particularly unruly May Days in recent years, but the observance is recognized around the globe.

There were gatherings in Los Angeles, Paris, Istanbul, Moscow, Manila and London on Sunday, some of which were also marred by violence.

May Day’s origins can be traced back to ancient times, when it was a Pagan festival celebrating spring.

May Day Fast Facts

But its history as a protest day is more recent – May 1 was declared “International Workers’ Day” by the International Socialist Conference following the violent protests in Chicago’s Haymarket Square in 1886.

Workers’ Day is a public holiday for most of the world, though the U.S. celebrates its Labor Day in September.

Protesters today still gather on May 1 to demand better working conditions.