Government official Pedro Ramos said 52 others were injured in the accident on Tuesday near the island capital of Funchal.


The tree fell while a large crowd was gathered as part of a traditional religious festival.

The Nossa Senhora do Monte festival is the island's biggest annual festivity.


It is held on August 14 and 15 and draws large crowds to a church on the outskirts of Funchal.


Portugal's prime minister expressed his condolences. Antonio Costa tweeted: "I express my condolences for the victims of the accident in Madeira."


He added that his "thoughts are with the family and friends of the victims".


Mr Costa said that the central government has made contact with local authorities on the island to offer its support.


He said that "the government has provided medical support given the high number of victims".


RTP public television showed images of emergency workers gathered under a group of tall trees on the Atlantic island.


Ambulances were shown pulling away from the site while workers wielding chainsaws cut away limbs from an enormous tree on the ground.


More televised images showed some people attending to the injured. Others appeared visibly shaken.


The regional government of Madeira has declared three days of mourning for the victims.


Local media reports said that the tree was an oak that was more than 200 years old.


Mr Ramos said that seven people had serious injuries and that of the 12 fatalities, 10 people died at the site of the accident. A child died en route to a local hospital, where another woman also died.