The 93-year-old's husband Prince Frederic von Anhalt told TMZ that the screen legend was admitted to hospital to have the lower half of her limb removed, in order to prevent a blood clot discovered in November from spreading.
He added that Gabor had refused practitioners' advice to return to hospital over Christmas, after she decided to spend what could be her last festive season in the comfort of her own home.
"She wanted to stay home and have a holiday," the Prince told People. "They wanted to do this before the holiday, but now the doctors have forced us."
The star's spokesperson John Blanchette added: "The doctors came to the house [on Sunday], and when they unwrapped the bandages, [they saw that] the wound had festered and they were afraid of gangrene developing, which would be life-threatening.
"She will lose the lower half of her leg below the knee. It's a dangerous operation, but the upside is that, if successful, she will remain her same old feisty self for a few more years."