Finnish police searched a reporter's home and seized her computer after she tried to destroy the hard drive to protect sources linked to a security story, her newspaper reported.

The journalist, Laura Halminen, said she tried to smash up her computer with a hammer in her home, but the laptop then started smoking and she called the fire brigade, according to an interview published by her employer Helsingin Sanomat.

Police officers who came to her home with the fire service to investigate the blaze then took her computer and searched her property, police said - a rare operation in a country rated high for protecting press freedom.

Officers had had to act quickly because they feared material linked to an investigation could be destroyed

The case centred on a story that Halminen and another journalist wrote on Saturday about a Finnish intelligence centre that they said monitored neighbouring Russia and, they reported, was about to get new powers to watch Finns online.

After the article's publication, Finland's President Sauli Niinisto released a statement saying authorities had launched an investigation into the leaking of material used in the story.

Halminen told her newspaper in the interview she had decided to destroy the computer "to make sure sources were protected in the best possible way".

On Sunday, the police's National Bureau of Investigation said, officers went to the property and found the computer burning in the basement. "After that, a special home search was ordered to be carried out in the apartment and basement," the force added.

It said officers had had to act quickly because they feared material linked to an investigation could be destroyed. There were no reports of anyone being arrested or charged.

The newspaper said the police also took phones and memory sticks in what it called a "very worrying" raid.

"A house search of this scale targeting a journalist is totally exceptional in Finland," editor-in-chief, Kaius Niemi, said.

Campaign group Reporters Without Borders ranked Finland third in its 2017 World Press Freedom Index, behind only Sweden and Norway.