Gilbert Baker, a San Francisco-based activist and artist best known for creating the rainbow flag representing gay rights, has died at the age of 65.

“My dearest friend in the world is gone. Clive Baker gave the world the rainbow flag, he gave me forty years of love and friendship,” Cleve Jones, a longtime friend, said on Twitter.

No details were immediately available on the cause of Baker’s death or where he died. According to the biography posted on his official website, he had been living in New York City.

Jones also tweeted a photo of Baker with President Obama, inviting mourners to meet him under a rainbow flag in the Castro district of San Francisco on Friday evening to remember his friend.

Former New York mayor Michael Bloomberg greets Gilbert Baker at the annual Gay Pride parade in New York City in 2002. Photograph: Jeff Christensen/Reuters

Baker, who was born in Kansas in 1951, was stationed in San Francisco in the early 1970s while serving in the US Army, at the start of the gay rights movement.

According to the website biography Baker began making banners for gay rights and anti-war protests, often at the request of Harvey Milk, who would become the first openly gay man elected to public office in California when he won the 1977 race for a seat on the San Francisco board of supervisors.

Milk rode under the first rainbow flags made by Baker at the San Francisco Gay Freedom Day Parade in June 1978, just months before the politician was murdered by a former city supervisor, the biography says.