Greta Thunberg clapped back at the German rail company Deutsche Bahn after it accused her of staging a picture of her sitting on the floor of one of its trains.

Deutsche Bahn appeared to suggest the photo was staged, saying Thunberg was treated to "friendly" and "competent" first-class service on its trains.

Thunberg responded in her typical no-nonsense fashion, saying she had in fact sat on the floor on two different trains before getting a seat after the train reached the German city of Göttingen.

The 16-year-old climate activist was traveling home from Madrid after attending the UN climate conference, a journey she made to and from Sweden on trains to avoid environmentally costly plane travel.

Visit Insider's homepage for more stories.

The teenage climate activist Greta Thunberg clapped back at a German rail operator after it appeared to accuse her of staging a picture in which she was seen sitting on the floor of what she called an "overcrowded" train.

Thunberg posted the picture on Twitter on Saturday, in which she could be seen sitting on the floor of the train and appeared to be wistfully staring out of the window surrounded by luggage.

The caption on the tweet said: "Traveling on overcrowded trains through Germany."

The German rail operator Deutsche Bahn responded to Thunberg noting that she had not praised its "friendly" and "competent" team and appearing to suggest that the photograph was staged by mentioning Thunberg had a first-class seat on the train.

Thunberg clapped back against Deutsche Bahn in her usual no-nonsense manner by relating her version of the story behind the picture.

"Our train from Basel was taken out of traffic," she said in a tweet. "So we sat on the floor on 2 different trains. After Göttingen I got a seat."

She also made it clear that her comment on the train being "overcrowded" was not a criticism against the operator.

"Overcrowded trains is a great sign because it means the demand for train travel is high!" she said.

Thunberg was traveling home from Madrid after attending the UN climate conference — a journey she made to and from her home in Sweden on public transport to avoid environmentally costly plane travel.

During the conference she was also criticized for saying politicians should be put "against the wall" to pass progressive environmental policies, a term some accused of insinuating violence.

Thunberg said the phrase was a literal translation from Swedish that means to put someone on the spot with tough questions, and she apologized for any misunderstanding.

The young activist is no stranger to high-profile Twitter spats, having last week incurred the wrath of US President Donald Trump, who said the decision to make her Time's Person of the Year was "ridiculous" and told Thunberg to "chill."