Dr. Jack Kevorkian, the Michigan physician who caused a storm of controversy with his advocacy for assisted suicide, has died.

Kevorkian, who was known by the nickname "Dr. Death," died between 2 and 2:30 a.m. Friday morning, the Detroit Free Press reports.

The 83-year-old had been hospitalized for about two weeks with kidney and heart troubles.

His lawyer, Mayer Morganroth, and Kevorkian's niece Ava Janus were reportedly by his side when he died.

Morganroth told media that Kevorkian appeared to have died from pulmonary thrombosis, but an official cause of death was not immediately determined.

"I had seen him earlier and he was conscious," said Morganroth, who added that the two spoke about Kevorkian's pending release from the hospital and planned start of rehabilitation.

"Then I left and he took a turn for the worst and I went back."

Kevorkian, who grew up in Pontiac, Michigan, died at the Beaumont Hospital in Royal Oak, a suburb of Detroit.

He first earned the nickname "Dr. Death" in the 1950s when he began advocating for prisoners on death row to become participants in painless medical experiments that would begin when they were conscious, but end in death.

In 1986 he again courted controversy by mounting a campaign around the benefits of euthanasia. Kevorkian even invented a suicide machine he called the Thanatron, which delivered a dose of saline, followed by a painkiller and finally a lethal dose of potassium chloride poison.

While neither the machine nor the concept was ever widely accepted by the medical community, Kevorkian eventually made headlines in the 1980s for his plan to set up a franchise of "obitoriums," where terminally ill patients could end their lives with the help of physicians.

But the most sensational media attention came in 1990, when Kevorkian helped Janet Adkins, a 45-year-old Alzheimer's patient, to end her own life.

Kevorkian assisted in her suicide inside his Volkswagen van in a public park, with Adkins dying of heart failure after Kevorkian administered a lethal dose of poison.

Kevorkian soon became an international celebrity over the incident, but was also charged in Adkins' murder. However, the charges were later dismissed due to a lack of clarity on Michigan's assisted suicide laws.

He continued helping terminal patients commit suicide, and his medical license was eventually suspended. However, Kevorkian continued his crusade despite laws that toughened various states' stance on assisted suicide.

He was in court numerous times, was jailed on occasion, and was eventually convicted of second-degree murder in 1999. Kevorkian was sentenced to 25 years in prison, but was released in 2007 after serving just over eight years of his sentence.

After his release Kevorkian continued his advocacy, joining the lecture circuit and speaking about his experiences with assisted suicide.