Greta Thunberg is seen at her home in Stockholm. Picture: BBC Radio 4 Today/Mishal Husain /via Reuters

Stockholm - Swedish teen climate activist Greta Thunberg turned 17 on Friday, but kept to her routine and stood outside parliament in Stockholm for her weekly protest.

"School strike week 72," she tweeted, posting a photo of herself holding a hand-painted sign that read "school strike for climate."

Thunberg staged her first school strike in August 2018.

Schools in the Swedish capital were on Friday still off for Christmas holidays.

Last month she returned to Sweden after being away for four and a half months.

While away from Sweden, Thunberg has spoken at climate meetings from Switzerland to New York, and most recently addressed the UN Climate Conference in Madrid and a rally in Turin, Italy.

In December, she was named Time magazine's person of the year for her role in creating a global movement to draw attention to climate change by skipping school on Fridays.

Thunberg doesn't fly for environmental reasons and completed two trans-Atlantic voyages in 2019.

From New York, where she spoke at a UN climate summit, Thunberg attended other engagements in Montreal, Canada, and then travelled across the US to Los Angeles.

Madrid took over as host city for the UN climate conference from Santiago, Chile, which was cancelled due to unrest in the South American country.