Six people have died and two others are missing after a series of explosions at a fireworks factory in northern Portugal, rescue workers said.

The explosions took place late yesterday and rescue workers were searching for more victims. President Marcelo Rebelo de Sousa travelled today to the village of Avoes, about 350 km north of Lisbon.

"In the name of the government I want to send my condolences and a word of consolation to the families of the victims," Prime Minister Antonio Costa said in a tweet.

Television images showed smoke and smouldering remains of the factory and the town declared three days of mourning for the victims.

Police launched an investigation into the explosions at the family-owned factory.

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