Activist Greta Thunberg sits on floor on homeward-bound German train

Berlin - Teen climate activist Greta Thunberg was headed back to her native Sweden without a seat on Saturday, tweeting a photo of herself sitting on the floor of a Deutsche Bahn train as she passed through Germany.

"Traveling on overcrowded trains through Germany. And I'm finally on my way home!" Thunberg wrote on her way from Frankfurt to Hamburg.

The 16-year-old, who doesn't fly for environmental reasons, was returning home after more than four months of travel over land and sea.

She has spoken at climate meetings from Switzerland to New York, and most recently addressed the UN Climate Conference in Madrid.

Some Twitter users responded to Thunberg by advising her to prepare for delays.

"Welcome to Germany, public transport here is chaos," one wrote. "A true deutsche bahn experience," another said.

Germany's rail service, Deutsche Bahn, answered by tweeting, "We wish #Greta a good trip home. And are working hard on more trains, connections and seats."

The state-owned company later addressed Thunberg directly in a tweet, taking her to task for failing to mention "how friendly and competent our staff were in looking after you in your first-class seat."

The exchange came as the rail service advertised that it is increasing the number of trains and connections and making climate-friendly travel more appealing.

Deutsche Bahn plays an important role in the government's climate protection targets, although there are often delays in the rail network. (dpa)