Neighbors of prominent US Senator Mitch McConnell have revealed alarming details about his health condition, which has remained unclear for about a month amid a lack of official updates from his team.

The Daily Beast reported that one of McConnell's neighbors in Washington noticed his condition deteriorating before June 14, the day he was found unconscious in his home and subsequently taken to the hospital.

The neighbor said he saw Senator McConnell, 84, sitting slumped in a wheelchair days before the incident, with his staff moving him, while he appeared pale, staring blankly with his mouth open.

Meanwhile, another neighbor living on the same street said she saw McConnell being loaded into an ambulance on June 14, while his staff appeared "visibly distraught" and "crying".

She added: "When he came out, I actually wondered if he had died. He didn't look good. He was unconscious, his eyes closed, and oxygen tubes were in his nose."

She continued: "I knew from his aides' constant coming and going that it was serious. There weren't many sirens, and that caught my attention."