SHANGHAI • Subway passengers on the Shanghai Metro system who take up space on morning peak-hour trains by sitting on portable stools have been criticised for their "rude and selfish" behaviour by Chinese netizens.

Shots of passengers on fold-up stools on Metro Line 9 drew the wrath of social media users, with some denouncing their selfishness in "thinking only about themselves" by taking up space in the cramped carriages, reported the South China Morning Post.

One user on microblog website Weibo said such behaviour could also be seen on other metro lines.

News website ThePaper.cn said the offending passengers showed no regard for standing commuters, who had to make room for them.

But other users argued that the metro was to blame for the shortage of seats, which had forced passengers to think up ways to avoid having to stand throughout the journey.

The metro operator said that it "neither encourages nor supports such behaviour", but added that passengers were allowed to bring small stools onto trains as luggage.

It warned that using the stools as seats annoyed other passengers and that there was a risk of accidents.

It posted photos of passengers seated on stools on its Weibo account, and urged others not to copy their actions. "Do behave yourselves - the metro is not your own home," it said.