Achebe was "a senior figure of African literature" at the time, he said, and it was "startling" how kind he was, and how "generous towards a younger, somewhat angrier writer."
"He was one of the most important writers to deal with the issue of the historical clash of civilizations, and the sometimes disastrous and sometimes benevolent consequences," Okri told CNN.
"He was without any doubt a very important figure, not only as a writer but as a guiding presence. He combined humility with forcefulness. He wrote clearly and truthfully, and was a touchstone for many African writers and many writers around the world."
'Generosity of spirit'
In the course of a long academic career, Achebe took up university posts in Nigeria and overseas, including teaching at Brown University in Rhode Island, where he was professor of Africana Studies, and Bard College in New York.
Leon Botstein, president of Bard College, paid tribute to Achebe as "a brilliant novelist, story-teller, and eloquent voice from the opposite side of Joseph Conrad, with respect to the relationship of the West to Africa."
He also highlighted Achebe's "extraordinary generosity of time and spirit" during more than 20 years as a member of the Bard College community, adding that he will be deeply missed.
"For many, he was considered the father of African literature, and for many of his students, he introduced them to an extraordinary literary tradition," Botstein said. "His importance to literature, and to those he taught and knew personally, will never be forgotten."
Corey D. B. Walker, an associate professor and chair of the department of Africana Studies at Brown University, said Achebe's loss was a great one.
"He was more than just a colleague, faculty member, and teacher at Brown. He was a gift to the world," he said.
"At a time like this we could draw many words of wisdom and comfort from the deep wells of various African cultures and traditions to honor him. The most fitting is the simple and elegant phrase, 'A great tree has fallen.' "
In an interview for the Paris Review of Books in 1994, Achebe spoke of how his early love of stories led him to realize that they reflected only the point of view of the white man. That spurred him to write himself.
"There is that great proverb -- that until the lions have their own historians, the history of the hunt will always glorify the hunter. ... Once I realized that, I had to be a writer. I had to be that historian," he said.
"It's not one man's job. It's not one person's job. But it is something we have to do, so that the story of the hunt will also reflect the agony, the travail -- the bravery, even, of the lions."