World-renowned author, poet and activist Maya Angelou has passed away, according to multiple media reports.

She was 86.

"She'd been very frail and had heart problems, but she was going strong, finishing a new book," Helen Brann, her literary agent, told ABC News. "I spoke to her yesterday. She was fine, as she always was. Her spirit was indomitable."

Angelou is most famous for her autobiographical book, "I Know Why The Caged Bird Sings," which has been a fixture in the literary world for decades.

She also was a respected writer of plays, TV shows and movies, as well as received more than 30 honorary doctorate degrees.

Angelou, who was born in 1928 in St. Louis, spoke six languages, was a close friend to Dr. Martin Luther King Jr. and even sang opera.