Grieving Brussels holds vigil at historic city square

"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 attacks on Tuesday.

Wrapped in the national flag and carrying candles and flowers, Belgians flocked by the hundreds by nightfall to the Place de la Bourse in the ancient heart of the city to mourn the dead.

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 too came after dark and European Commission president Jean-Claude Juncker also paid homage to the dead.

"Tonight I am Belgian," an emotional Juncker said.

"It's sad, it's unfortunate, it's shocking," said Sofiane, an Algerian student, who had come to pay her respects.