Firefighters cover victims of a tree that toppled into worshipping crowds during a religious festival in Funchal, Madeira island on Tuesday (15 August 2017). Reuters

A falling tree has killed at least 13 people including two children on the Portuguese island of Madeira.

The tree crashed down on a square in the main town Funchal while people were celebrating a religious ceremony. There are thought to be at least 52 people injured.

The tree came down on Fountain Square around midday local time on Tuesday (15 August), which was a public holiday in which people had gathered to celebrate the feast of the Assumption in the Lady of the Mount festival.

One unnamed eyewitness said according to the Funchal town website: "I heard a great noise and when I looked at the tree it was already falling but was too fast and people started to run and those who couldn't run stayed under the tree."

Another witness said: "It was something we will never forget. It sounded like shots and it just gave us time to look and run away when we realised there were people under the tree."

Authorities said that there were French, German and Hungarian citizens among the injured.

Local reports suggested that the tree was 200 years old and had been shored up for at least two years because the trunk was hollow.

The Portuguese prime minister António Costa offered his condolences to the victims and there will be three days of mourning for the disaster.