Nigerian Nobel laureate Wole Soyinka has said the US revoked his visa and banned him from the country.

The 91-year-old author, who won the Nobel Prize for literature in 1986, said the US consulate asked him to bring in his passport so his visa could be cancelled in person as new unspecified information had come to light.

Soyinka called the invitation a "rather curious love letter from an embassy" in a news conference held on Tuesday and told organisations hoping to invite him to the US "not to waste their time".

The US embassy in Nigeria has said it cannot comment on individual cases.

The Nobel laureate has previously held permanent residency in the US but renounced it in 2016, tearing up his green card in protest of President Donald Trump's election.

The green card is a permanent residence permit for the US - prized by many African immigrants to the US.

Soyinka affirmed on Tuesday that he no longer had his green card – and jokingly added that it had "fallen between the fingers of a pair of scissors and it got cut into a couple of pieces".

The famed author has had regular teaching engagements at US universities for the past 30 years.

"I have no visa. I am banned," he said on Tuesday.

Soyinka has long been critical of the Trump administration's radical stance on immigration and linked the visa revocation to his outspoken criticism.

He said his recent comparison of Trump to Uganda's dictator - "Idi Amin in white face" - may have contributed to the current situation.

"When I called Donald Trump Idi Amin, I thought I was paying him a compliment," Soyinka said, "he's been behaving like a dictator."

Idi Amin was a Ugandan military officer and dictator who ruled the country from 1971 to 1979, infamous for his brutal regime and widespread human rights abuses.

When asked if he would consider going back to the US, Soyinka said: "How old am I?"

In July, the US State Department announced sweeping changes to its non-immigrant visa policy for citizens of Nigeria and several other African countries.

According to the policy, nearly all non-immigrant and non-diplomatic visas issued to Nigerians and nationals of Cameroon, Ethiopia and Ghana would now be single-entry and valid for only three months, rolling back the up to five-year, multiple-entry visas they had enjoyed previously.