In the wake of the deadly terror attack in Barcelona, Spanish political leaders, celebrities, royals, and ordinary people have started to post images of a looped black ribbon to mourn the victims.

Many are also using the hashtag #TotSomBarcelona – we are all Barcelona.

They include Spanish Prime Minsiter Mariano Rajoy:

Ribbons have been used as a sign of mourning and defiance in Spain since at least the 1990s, and are a familiar sight from the aftermath of attacks by Basque separatist group ETA.

Barcelona FC star Leo Messi also posted a ribbon:

http://instagr.am/p/BX57aOGFoWa

"We won't give in, those of us who wish to live in a peaceful, hate-free world in which respect and tolerance form the basis of our coexistence are in the overwhelming majority," Messi wrote in his caption.

Here's Spain's national police service:

And the European Commission's Spanish-language account:

Barcelona football club:

http://instagr.am/p/BX58ZDEnJ8W

La Liga rivals Malaga:

And an ordinary Spaniard:

A white ribbon against a black background was also featured on the front page of daily newspaper La Razón on Friday:

Foto: The front page of La Razón newspaper on Friday. source La Razon

Following four bomb attacks on commuter trains in Madrid in 2004, which killed 191 people, people attached or painted black ribbons onto the Spanish flag, pinned black ribbons to their clothes, and hung black ribbons outside their businesses, NBC News reported at the time. People in France and Germany also wore black ribbons in solidarity.

Real Madrid black ribbon mourning after Madrid 2004

Foto: Real Madrid supporters carry a Spanish flag with a black ribbon during a minute of silence at the team's Santiago Bernabéu stadium following the Madrid bombings in 2004. source Reuters

The black ribbon has been used to signify solidarity in the face of terrorism in other countries since.

Google added a black ribbon to its search pages after an attack on Charlie Hebdo's offices in Paris claimed 12 lives in 2015. After a suicide bomber killed 22 people at an Ariana Grande concert at Manchester Arena this May, social media users fashioned a black ribbon with Grande's signature bunny ears in solidarity.

http://instagr.am/p/BUaySBUl7Q1