Muslim activist and author Yassmin Abdel-Magied claims she has been deported from the United States after being refused entry by immigration officials at an airport.
The 27-year-old Sudanese-Australian, who recently moved to London, flew into Minneapolis on Wednesday night, local time, but just three hours later was ordered onto another plane out of the US.
She had been due to deliver a speech about fighting online hate at the Pen America World Voices Festival in New York on April 21.
Ms Abdel-Magied took to Twitter while being detained by immigration officials at Minneapolis airport, saying they had "taken my phone, cancelled my visa and are deporting me".
"Interesting facts: within a few min of looking at my case the border security person - Officer Herberg looking at my case she announces: 'we're sending you back!'," she tweeted.
"Well, guess that tightening of immigration laws business is working, despite my Australian passport. We're taking off now. What a time..."
Ms Abdel-Magied said the airport officials also took her passport.
"Apparently I can't be trusted with it until I'm in a foreign country because, as Officer Blees said, 'planes get turned away back way too often and then...," she tweeted.
Ms Abdel-Magied did not say which country she had been in before flying into the US or where she was now headed.
She moved to London in 2017 after making a series of controversial claims including that "Islam to me is the most feminist religion".
She also suffered a public backlash after her Anzac Day post on social media which said: "Lest We Forget (Manus, Nauru, Syria, Palestine ...)".
The post was deleted from her Facebook page a few hours later, with Ms Abdel-Magied apologising and acknowledging "that the timing and nature of the post was disrespectful'.
Her apparent deportation from the US comes after the US Supreme Court last December gave the green light to President Donald Trump's controversial travel ban that targets people from six Muslim-majority countries.
The ban was subject to several legal challenges after opponents said it was in violation of the US Constitution because it discriminates against Muslims.
Asked to comment.Australia's Citizenship and Multicultural Affairs Minister Alan Tudge said US visas were a decision for the American government.
"At the end of the day it is unusual for an Australian citizen to not be granted a visa to go into the United States, but I simply don't know the details behind this particular case," he said.
"I just don't know the details underpinning this and whether or not it was that she had a tourist visa, that perhaps there was evidence she was planning to do other things other than being a tourist there."