Malmö, Sweden - Swedish climate campaigner Greta Thunberg was fined on Monday for disobeying police at a rally last month, but said she acted out of necessity due to the climate crisis.

The 20-year-old appeared in court in the southern Swedish city of Malmö after 11:00 AM on Monday.

The activist "took part in a demonstration that disrupted traffic" and "refused to obey police orders to leave the site," according to the charge sheet seen by AFP.

"It's correct that I was at that place on that day, and it's correct that I received an order that I didn't listen to, but I want to deny the crime," Thunberg told the court when asked about the charge against her.

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Thunberg said she had acted out of necessity, citing the need created by the "climate crisis."

"According to me we are in an emergency, and then due to that my action was legitimate," the climate campaigner told reporters after the trial.

After a short trial, the court nonetheless found that she was still liable for her actions and sentenced her to pay a fine of 1,500 kronor ($144) plus an additional 1,000 kronor to the Swedish fund for victims of crime.

The crime she was convicted of can carry a maximum sentence of six months in prison, but usually these types of charges result in fines.

The rally, organized by environmental activist group "Ta tillbaka framtiden" (Reclaim the Future), tried to block the entrance and exit to the Malmö harbor to protest against the use of fossil fuels.

Asked if she would exercise more caution in the future following her fine, Thunberg said she was "definitely not going to back down."

"We know that we cannot save the world by playing by the rules because the laws have to be changed," the activist said.

"It is absurd that the ones acting in line with the science, the ones blocking the fossil fuel industry are the ones having to pay the price for it," she added.

Thunberg shot to global fame after starting her "School Strike for the Climate" in front of Sweden's parliament in Stockholm at the age of 15.

She and a small band of youths founded the Fridays for Future movement, which quickly became a global phenomenon.

In addition to her climate strikes, the young activist regularly lambasts governments and politicians for not properly addressing climate issues.

Reclaim the Future insists that despite the legal pressures, it remains unbowed in its determination to stand up to the fossil fuel industry.

"If the court chooses to see our action as a crime it may do so, but we know we have the right to live and the fossil fuels industry stands in the way of that," the group spokesperson Irma Kjellstrom told AFP.

Six members of the organization would be appearing in court in Malmö, she said.

"We young people are not going to wait but will do what we can to stop this industry which is burning our lives," she said, explaining the group's plans for continuing civil disobedience.