Paris, April 18 -- Bells of cathedrals across France rang in a moving tribute Wednesday to Notre Dame as firefighters and experts continued to keep the beloved but weakened landmark under close surveillance.

From Sacre Coeur in Paris to the cities of Strasbourg in the east and Rouen in the west, the architectural treasures of France solemnly marked the inferno, two days after it ravaged the gothic cathedral, widely regarded as the soul of France.

"I just arrived for the first ring of the bells and immediately there was an emotion. Incredible, indescribable, I just can't explain it," said Nadia Pascassio-Comte, in Strasbourg. "It was beautiful and sad at the same time. I had tears in my eyes at one point, and I think that this solidarity...