Canadian poet Margaret Avison, described as "one of the great religious poets" of the 20th century, has died at age 89.

Avison died last week in Toronto. No cause of death has been released.

Avison won the prestigious Griffin Poetry Prize four years ago and was twice winner of the Governor General's Award for poetry in a literary career that spanned 40 years.

Her first book of poetry, The Winter Sun, was published in 1960 and she became a "committed Christian" in 1963, often writing about her faith.

Many critics compare her work to the great metaphysical poets of the 17th century.

"It was a private religious conviction," said Joseph Zezulka, an English professor at the University of Western Ontario and friend of Avison.

"She was kindliness itself. She had so much tolerance and charity for her fellow beings, and I think that's the important thing about her Christianity.

"Her contribution to Canadian literature was incalculable," he said, adding that she had an international following.

Avison was born in Galt, Ont. in 1918 and spent her childhood in Regina and Calgary.

She attended the University of Toronto's Victoria College, where she studied English literature. She went on to hold three honorary doctorates.

She also worked as a librarian, editor, teacher and social worker. Zezulka met her in the early 1970s while she was a writer-in-residence at Western.

The Winter Sun and 1998's No Time both won Governor General's Awards.

After the publication of Concrete and Wild Carrot in 2003, she won the $40,000 Griffin prize.

The judges hailed Avison for the "many decades she has forged a way to write, against the grain, some of the most human, sweet and profound poetry of our time."

She also published Momentary Dark, The Dumbfounding and Not Yet But Still.

Zezulka said reading Avison's poetry required persistence and sometimes hard work. 

"The thing with her poetry is that you must grapple with it, it just does not open up. Its rewards come only to those are willing to make the effort," he said.

"Her poems were not snacks, they were full meals."

Avison was made officer of the Order of Canada in 1985.