Mystery surrounds Gold Star father Khizr Khan's claim that his 'travel privileges are being reviewed' as immigration authorities deny being involved in the alleged situation.

Khan, whose 27-year-old son US Army Captain Humayun Khan died while serving in Iraq in 2004, first said he was notified on Sunday that he could not travel to Canada where he had planned to deliver a speech on 'tolerance, understanding, unity and the rule of law'.

The Gold Star father has been a vocal critic of President Donald Trump, and the announcement of him canceling his trip to Toronto coincided with the president's rewritten order to temporarily ban entry of citizens from six Muslim-majority nations to the U.S.

Khan, who gained world-wide attention last year during the Democratic National Convention where he argued Trump's proposed travel ban was immoral and unconstitutional, has been a U.S. citizen for more than 30 years.

In addition, he was born in Pakistan which is not one of the six countries on Trump's list. Officials with several government agencies both in the U.S. and Canada have denied being involved.

Mystery surrounds Gold Star father Khizr Khan's (above) claim that his 'travel privileges are being reviewed' as immigration authorities deny being involved in the alleged situation. Khan has not revealed which U.S. agency contacted him about his travel privileges

The news was announced on the Facebook page of Ramsay Talks, the event where Khan was scheduled to deliver a speech on 'tolerance, understanding, unity and the rule of law' on March 7th

Ramsay Talks, the organizer of the event Khan was scheduled to speak at on March 7 posted a message on Facebook notifying attendees of his cancellation and providing the reason why from Khan.

'This turn of events is not just of deep concern to me but to all my fellow Americans who cherish our freedom to travel abroad,' said Khan, according to the post.

'I have not been given any reason as to why. I am grateful for your support and look forward to visiting Toronto in the near future.'

However, Khan did not reveal which U.S. agency contacted him.

Bob Ramsay, the organizer of Ramsay Talks, said on Tuesday that he didn't know the details surrounding Khan's claim.

'I don't know exactly who conducted the review, but in speaking with Mr. Khan, it was certainly U.S. authorities,' Ramsay told The Washington Post. 'That's all I know.'

Khan (right) gained international attention following a speech at last year's Democratic National Convention, where he argued that then-Republican presidential candidate Donald Trump's proposed travel ban was immoral and unconstitutional

News of Khan's travel restrictions followed the release of President Trump's executive order banning travel from six Muslim-majority countries that won't go into action until later this month

Khan has still not further explained his allegation or responded to questions from DailyMail.com or other media outlets.

In addition, his claim about being prevented to travel abroad raised doubts from many, as no visa is needed to travel to Canada and U.S. citizens are not prevented from traveling abroad.

Representatives with US Citizenship and Immigration Services told Dailymail.com that they were not aware of Khan's case or of any American citizen having their travel privileges put under review by the US government.

US Customs & Border Protection officials said the agency does not contact travelers in advance of their travel out of the US, adding that any US citizen with a passport may travel out of the country.

The agency told Reuters that it would not comment specifically on the Khan case, citing privacy protections.

Khan's son, 27-year-old US Army Captain Humayun Khan, (above) was killed by a suicide bomber in 2004 during the Iraq War and was posthumously awarded a Bronze Star and Purple Heart

There is no US State Department procedure for reviewing 'travel privileges', an agency official told the New York Daily News. Anyone with a valid American passport can enter and leave the country, they added.

The Canadian foreign ministry also denied that they issued a review of Khan's ability to travel to the country.

'We are unaware of any restrictions regarding this traveler,' Camielle Edwards, spokeswoman for Canada's Immigration Minister Ahmed Hussen told the Post.

The U.S. government cannot prevent those holding passports from traveling if they have not committed a crime, and per public records, Khan does not have a criminal history.

It is unclear who called for the review or the grounds for it.