Yoko Ono urges gun control on 40th anniversary of John Lennon's death

"The death of a loved one is a hollowing experience," tweeted the 87-year-old artist, who still lives in the Dakota building in Manhattan outside of which her husband was shot four decades ago.

"After 40 years, Sean, Julian and I still miss him. 'Imagine all the people living life in peace,'" she wrote, quoting the 1971 song she co-wrote with Lennon that became the best-selling single of his solo career.

Ono, who witnessed her husband's murder at close range, also tweeted an image of the former Beatle's shattered and bloodied spectacles, which included the words: "Over 1,436,000 people have been killed by guns in the U.S.A. since John Lennon was shot and killed on December 8, 1980."

At 40 years old, Lennon had returned to songwriting shortly before his death, having taken a five-year hiatus to raise his young son Sean.

The couple was returning home to New York's famous Dakota building across from Central Park, when disgruntled Beatles fan Mark David Chapman shot Lennon dead.

"Tell me it isn't true!" Ono cried in horror.

After Lennon's murder, Ono committed to preserve his memory, funding the construction of the Strawberry Fields memorial in New York that's become a point of pilgrimage for fans and mourners across the globe.

By mid-morning Tuesday, a shrine featuring flowers, photos and a small holiday tree had already cropped up on the "Imagine" mosaic that anchors the memorial in Central Park.

In her tweet commemorating Lennon's death, Ono included a number of hashtags including #guncontrol now and #end gun violence.

She also hashtagged the National Rifle Association, the powerful US organization that has for decades battled to loosen and eliminate firearms control legislation.