Greta Thunberg has apologised for saying world leaders should be "put against the wall" in a speech.
The teenage climate activist made the comment while addressing a Fridays For Future protest in Turin, Italy.
In English the phrase is associated with execution by firing squad, but Ms Thunberg said it had a different meaning in her native language Swedish.
"That's what happens when you improvise speeches in a second language," she added on Saturday.
Ms Thunberg was speaking in Turin after attending the UN climate summit COP25 in the Spanish capital Madrid.
She said she feared the summit alone would not lead to adequate climate action, and that activists should continue to take world leaders to task.
"World leaders are still trying to run away from their responsibilities, but we have to make sure they cannot do that," she said.
"We will make sure that we put them against the wall, and they will have to do their job to protect our futures."
After some initial concern over her use of the phrase - which usually means to execute people by firing squad, against a wall - she tweeted a clarification.
"Yesterday I said we must hold our leaders accountable and unfortunately said 'put them against the wall'," she wrote.
"That's Swenglish: 'att ställa någon mot väggen' (to put someone against the wall) means to hold someone accountable."
She continued: "Of course I apologise if anyone misunderstood this. I cannot enough express the fact that I - as well as the entire school strike movement - are against any possible form of violence. It goes without saying but I say it anyway."
As she travelled back from Madrid on Saturday, the climate activist was involved in a much-commented-on exchange with German rail authorities, after she posted a picture of herself sitting on the floor of an overcrowded train.
Traveling on overcrowded trains through Germany. And I’m finally on my way home! pic.twitter.com/ssfLCPsR8o— Greta Thunberg (@GretaThunberg) December 14, 2019
Deutsche Bahn issued a statement - and tweets - thanking the activist for supporting the railway workers in their fight against climate change.
The company suggested, however, that it would have appreciated it if she had also highlighted the fact that she was eventually given a seat in the first-class carriage, and treated very well there.
In her subsequent response, Ms Thunberg denied she had been complaining with her picture, saying overcrowding was a good sign of high demand.
Our train from Basel was taken out of traffic. So we sat on the floor on 2 different trains. After Göttingen I got a seat.This is no problem of course and I never said it was. Overcrowded trains is a great sign because it means the demand for train travel is high!— Greta Thunberg (@GretaThunberg) December 15, 2019
Ms Thunberg was recently named Time magazine's youngest ever Person of the Year, for inspiring a global movement to fight the climate crisis.