The 83-year-old is being looked after by relatives in Egypt, where he lives.
“He was diagnosed with Alzheimer’s a while ago,” agent Steve Kenis told AFP adding: “It’s a serious disease and he hadn’t been been able to take any work for many months.”
“He’s under the care of his family,” he said.
The agent confirmed news first reported by the Spanish daily El Mundo, which cited the actor’s son Tarek.
“I don’t want to comment on this issue,” the son told AFP by phone from Canada.
Known for his charismatic good looks and bridge-playing prowess, Sharif is resting at his home in Egypt, according to the Los Angeles Times newspaper.
Born in 1932 the son of a lumber merchant in Egypt’s second city Alexandria, Sharif was nominated for an Academy Award in 1963 for his role as Sherif Ali in “Lawrence of Arabia.”
The actor, fluent in English, Arabic, Spanish, Italian, Greek and French, also won Golden Globes for “Lawrence of Arabia” and “Doctor Zhivago.”
Sharif, who was raised a Roman Catholic but later converted to Islam, started acting in the 1950s and had his most high-profile roles in the 1960s, when he also starred in “Funny Girl” opposite Barbra Streisand in 1968.
He kept working over the following decades, often in TV movies, while also earning a reputation as one of the world’s best known contract bridge players.
He co-wrote a syndicated bridge newspaper column in the 1970s and 80s, as well as authoring several books and a bridge computer game, “Omar Sharif Bridge.”
The actor made something of a comeback in 2003 in the title role of the French film Monsieur Ibrahim (2003) in which he played an elderly Muslim shopkeeper.
The performance won him a best actor award at the Venice Film Festival and the best actor Cesar, France’s equivalent of an Oscar.
Sharif underwent triple heart bypass surgery in 1992 and suffered a mild heart attack in 1994, according to the IMDb movie database website. He smoked 100 cigarettes a day but quit after the operation.
In January this year, Sharif’s actress ex-wife Faten Hamama died aged 83 after a career spanning seven decades and almost 100 films alongside masters of Egypt’s film industry. She was buried at her family cemetery in Cairo.