It is believed Prince died after overdosing on painkillers.

Following news of Prince’s untimely death on Thursday, unconfirmed reports suggest the pop superstar suffered a drug overdose in the week prior to his passing.

According to a report from TMZ, the superstar overdosed six days ago, and his jet had to make emergency landing in Illinois so he could receive a life-saving injection.

The “save shot” was comprised of drugs given to counteract the effects of an opiate, TMZ reports.

The report also claims that Prince refused to stay in hospital because he couldn’t get a private room, despite doctors advising him to stay overnight.

Prince performs during the "Pepsi Halftime Show" at Super Bowl XLI on February 4, 2007  in Florida. (Photo: Getty)

Sources allegedly told The Daily Mail the drug on which Prince overdosed was a highly addictive painkiller called Percocet.

The megastar began taking Percocet pills years ago because of a chronic hip problem caused by decades of vigorous stage performances.

Despite needing to use a cane to walk, he refused to have the double hip replacement he needed  because of his religion, The Daily Mail reports.

The surgery would have required a blood transfusion, but the procedure is forbidden under Prince's Jehovah's Witnesses faith.

With his first wife, backup singer Mayte, on stage. (Photo: Getty)

Though the cause of death has not yet been officially confirmed, Prince had been unwell for several weeks. His representatives said he had been battling the flu, but some fans questioned whether a flu would be serious enough to cause his private jet to make an emergency landing.

Following speculation about his health, the pop superstar appeared at a dance party at his estate in Minneapolis on Saturday to "prove" he was still alive.

"Wait a few days before you waste any prayers," he told fans at the event.

He was then spotted at a Walgreens pharmacy on Wednesday evening looking "frail and nervous," TMZ reports. It was reportedly the his fourth trip to the pharmacy in the space of one week.

Prince sold more than 100 million records during his four-decade musical career - but the stage performances left him with a hip problem that he allegedly needed to treat with the addictive painkiller Percocet.

The legendary singer, who sold more than 100 million records, was found unresponsive in an elevator on Thursday morning.

A 911 dispatcher reportedly told one of the paramedics who rushed to his Minnesota estate: "Male down, not breathing."

Paramedics and police tried to revive him, but he died in his estate, Paisley Park, at 10:10am yesterday. He was 57.

An autopsy is being performed to confirm the cause of his death.