Hours after a grisly terror attack rocked Brussels' airport and a downtown metro stop, #JeSuisBruxelles and #JeSuisBrussels were trending on Twitter in a sign of solidarity with victims.

The hashtag, which means "I am Brussels," began trending worldwide following the attacks which killed at least 26 and wounded 130 people.

On social media people are all too familiar with the hashtag, which is a nod to #JeSuisCharlie that was used after the terror attack at the satirical newspaper Charlie Hebdo. Many expressed their horror on social media that once again they were watching attacks unfold in a European city.

Following the attacks, terror alerts rose across Europe, in the U.S. and around the world.

Belgium's federal prosecutor confirmed the blasts at the airport were caused by a suicide attack. The explosion at the metro station was near buildings that house European Union institutions in central Brussels.

"I strongly condemn these hateful attacks. Our thoughts go out to the victims and their families. We stand united against terrorism," Belgian Prime Minister Charles Michel said in a tweet.