Paris - U.S. President Donald Trump has tweeted about the fire engulfing Paris’ iconic Notre Dame Cathedral.

Trump wrote on Twitter after the fire broke out Monday: “So horrible to watch the massive fire at Notre Dame Cathedral in Paris” and made suggestions for how first responders should tackle it.

He said: “Perhaps flying water tankers could be used to put it out,” adding: “Must act quickly!”

Firefighters were trying to contain the fire when the cathedral’s spire collapsed. Authorities say the wooden interior now is burning.