Brussels holds vigil at historic City Square, Belgium to observe 3-day mourning

Brussels: "Brussels I love you" says the message written in chalk on a historic city square, a place for raucous celebration that has become a scene of grief after Belgium's worst terror attack.

Wrapped in the national flag and carrying candles and flowers, Belgians flocked in their hundreds to the Place de la Bourse in the ancient heart of the city to grieve as the country held three days of national mourning.

The Belgian capital, home to the European Union headquarters, was left reeling Tuesday after some 35 people were killed in bombings at Zaventem Airport and on a metro train.

(from top L) Brandenburg Gate in Berlin, Eiffel Tower in Paris, Town council building in Belgrade, Trevi Fountain in Rome, Royal Palace at Dam Square in Amsterdam and Rome's Campidoglio. (Photo: AFP)

A lone musician played a cello as a mourner waved a banner reading "United against hate" and another message scrawled on the ground said: "Christians + Muslims + Jews = humanity".

"It's important to get together after moments like these," Leila Devin, 22, told AFP. "It shows we're united against terror."

Belgian Prime Minister Charles Michel joined the mourners after dark fell and European Commission president Jean-Claude Juncker also paid homage to the dead.

People light candles in tribute to victims at a makeshift memorial in front of the stock exchange at the Place de la Bourse. (Photo: AFP)

"Tonight I am Belgian," he said, full of emotion.

Landmarks around the world, including the Eiffel Tower in Paris to Berlin's Brandenburg Gate, were lit up in the black, yellow and red of Belgium's national flag in solidarity.