CAIRO — As an ailing Libyan commander lies in a Paris hospital, his condition a carefully guarded secret, speculation about his fate has created a power vacuum in eastern Libya, stoking fears of a violent succession feud that could plunge Libya into turmoil again.

Since the news broke 10 days ago that the commander, Gen. Khalifa Hifter, had been airlifted to France from Jordan for emergency treatment, Libya’s rumor mill has gone into overdrive amid news reports that the general, a 75-year-old strongman who controls most of eastern Libya, was seriously ill, incapacitated or even dead.

General Hifter’s aides denied the reports, insisting that he had been hospitalized for a routine checkup, and they promised that he would soon be back in Benghazi, his eastern stronghold where he nurtured ambitions of national power.

But an explosion in the city on Wednesday suggested that tensions there could soon overtake the bedridden general.