Pamela Geller
Pamela Geller is the head of the American Freedom Defence Initiative, which sought to post the cartoon. Facebook

Taking pre-emptive action to dodge expected outrage from Muslims, Washington DC subway officials are blocking the display of a cartoon of the prophet Mohammad from the transit system by prohibiting all "issue-oriented" advertisements.

The blanket ban is an apparent bid to avoid a free-speech court challenge, a similar tactic taken earlier this year in New York. The ban, passed unanimously by the board of directors of the Washington Metropolitan Area Transit Authority, prohibits political, religious and advocacy ads through the end of the year, a spokesman told Reuters.

The American Freedom Defense Initiative had asked to buy space to display the cartoon, which won first place at a provocative "Draw Mohammad" event in Texas earlier this month where two Islamic State (Isis) sympathisers were shot dead by police when they attempted to attack the building.

The ad, which calls for Americans to support free speech, features a bearded, turban-wearing Mohammad waving a sword and shouting: "You can't draw me!" In reply, a cartoon bubble reveals an artist grasping a pencil and saying: "That's why I draw you."

Pamela Geller, the controversial leader of the American Freedom Defence Initiative, blasted the ban on her website. "," she writes. "These cowards may claim that they are making people safer, but I submit to you the opposite. They are making it far more dangerous for Americans everywhere."

Nihad Awad, head of the Council on American Islamic Relations, said Geller and her group were "using free speech... to divide people".

Last month, New York's Metropolitan Transit Authority decided to ban all political ads after losing a court battle with the same group after it banned an ad that read: "Hamas Kills Jews."

Geller's organisation, which has been identified as a hate group by the Southern Poverty Law Center, has posted controversial ads in Philadelphia, San Francisco, Chicago, and previously in the Washington subway system three years ago.