Milton Glaser, the influential American graphic designer who created the "I ♥ NY" logo, has died aged 91.

Made for a 1977 tourism campaign, the logo rapidly gained recognition across the world and has been described as the most frequently imitated in history.

Glaser later said he was "flabbergasted by what happened to this little, simple nothing of an idea".

He also created a famous poster of Bob Dylan with psychedelic hair and was a co-founder of New York magazine.

The cause of his death was a stroke, his wife Shirley told the New York Times.

Glaser was born in the Bronx borough of New York City in 1929. He studied at the Cooper Union for the Advancement of Science and Art, a college in Manhattan, and at the Academy of Fine Arts in Bologna, Italy.

In 1954, Glaser set up Push Pin Studios with three Cooper Union classmates and helped bring a new visual language to commercial art, seeking inspiration from everything from Art Nouveau to Chinese wash drawing, German woodcuts, and the cartoons of the 1930s.

His poster of Bob Dylan featured a silhouette of the musician based on a self-portrait by Marcel Duchamp and brightly coloured locks of hair borrowed from Islamic art.

The poster was included in Dylan's 1967 album Greatest Hits, which was bought by six million fans, and adorned countless walls.

In 1968, Glaser co-founded New York magazine and was its design director for nine years.

"Around our office, of course, he will forever be one of the small team of men and women that, in the late sixties, yanked New York out of the newspaper morgue and turned it into a great American magazine," the magazine's obituary said.

In 1974, he established his own design firm, Milton Glaser, Inc.

Three years later, he designed the "I ♥ NY" logo free of charge to help promote tourism in his home city, amid a crime wave and financial crisis. He came up with the idea while riding in a taxi and scribbled it in red crayon on an envelope, which is now in the permanent collection of the Museum of Modern Art (MoMA).

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"It is one of those peculiarities of your own life where you don't know the consequences of your own actions," he told the New York Times in 2008. "Who in the world would have thought that this silly little bit of ephemera would become one of the most pervasive images of the 20th Century?"

After the 9/11 attacks, Glaser released an amended version of the logo that featured a bruised heart and read "I ♥ NY MORE THAN EVER".