Swedish climate activist Greta Thunberg said Friday she was marking her last "school strike" as she was graduating high school, but said she would continue partaking in weekly protests.

"Today, I graduate from school, which means I'll no longer be able to school strike for the climate. This is then the last school strike for me," Thunberg said in a post on social media.

Thunberg, who spearheaded the global Fridays for Future movement, also said she didn't plan on giving up the protests completely.

"I'll continue to protest on Fridays, even though it’s not technically 'school striking'. We simply have no other option than to do everything we possibly can," said the 20-year-old, adding "the fight has only just begun."

Greta Thunberg was only 15 when she began her "School strike for climate" in front of Sweden parliament in Stockholm.

"When I started striking in 2018 I could never have expected that it would lead to anything," she said in a statement.

Together with a small group of youths she founded the Fridays for Future movement, which quickly became a global phenomenon.

"During 2019, millions of youth striked from school for the climate, flooding the streets in over 180 countries," Thunberg said.

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

At the end of March, she condemned what she called an "unprecedented betrayal" from  leaders after the publication of the latest report by the IPCC, the UN's climate advisory panel.