Tributes are flowing from around the world after the deadly attacks in Brussels that have killed at least 30 people and injured more than 200.
Berlin's Brandenburg Gate, Rome's Trevi Fountain, the Eiffel Tower and Lyon's courthouse have been lit up with the colours of the Belgian flag in a show of solidarity.
"We are united," Paris Mayor Anne Hidalgo said in a tweet announcing the special Eiffel Tower illuminations.
At French President Francois Hollande's official residence, the French tricolour flew at half-mast and Belgian flags stood at the main entrance.
On social media, images of a tearful Tintin, the cartoon hero created by Belgian writer Herge, have been shared as a symbol of solidarity.
Islamic State claimed responsibility for the assaults on Brussels airport and a metro train earlier on Tuesday -- a stark reminder of the shootings and suicide bombings which killed 130 people in Paris last November and which were also claimed by the militant Islamist group.
The blasts in Brussels occurred four days after the arrest in the Belgian capital of a suspected participant in the Paris attacks. Police in both capitals had been on alert for post-arrest reprisals.