A 104-year-old Australian biologist who drew international attention to his right-to-die case ended his life in Switzerland on Thursday, an advocacy group said.

Exit International, the group that helped David Goodall carry out his wish, said the scientist was declared dead at 12:30 p.m. in Liestal, a town outside the city of Basel, where he had traveled to take advantage of Switzerland's assisted-suicide laws.

"I no longer want to continue life," Goodall told reporters Wednesday.

"My life has been rather poor for the last year or so. And I'm very happy to end it," he said Thursday in the room where he died shortly after.

The British-born scientist said this week that he had been contemplating the idea of suicide for about 20 years, but only started thinking about it for himself after his quality of life deteriorated over the last year.

He cited a lack of mobility, doctor's restrictions and an Australian law prohibiting him from taking his own life among his complaints, but he was not ill.

Assisted suicide is legal in Switzerland, where the procedure is available for anyone who acknowledges in writing that they are taking their lives willingly — without being forced. But the practice is frowned upon by many doctors and some others who say it should be reserved for the terminally ill. Goodall and his supporters want the practice to be more accepted as a legitimate choice for elderly people in sound mind.

On Wednesday, Goodall told a crowded news conference that medically assisted suicide should be more widely available.

"At my age, and even at rather less than my age, one wants to be free to choose the death and when the death is the appropriate time," he said.

Hundreds of people — some far more frail than Goodall, who used a wheelchair — travel to Switzerland every year to take their lives. The best-known group to help foreigners end their days in the Alpine country is Dignitas, but others include Life Circle in Basel, Goodall's choice.

Goodall took his life with an intravenous drip of pentobarbital, a chemical often used as an anesthetic but which is lethal in excessive doses. A doctor put a cannula in his arm, and Goodall turned a wheel to allow the solution to flow, Exit International said.

Philip Nitschke, director of Exit International, said that before activating the drip, Goodall had to answer "several questions so he knew who he was, where he was and what he was about to do."

"He answered those questions with great clarity, activated the process" while Beethoven's Ninth Symphony played in the background, he added.

His last words before losing consciousness were "this is taking an awfully long time," Nitschke said, but "he died shortly thereafter."

Exit International said Goodall had requested that his body be donated to medicine, or his ashes sprinkled locally.

"He wishes to have no funeral, no remembrance service or ceremony," the group said in a statement. "David has no belief in the afterlife."

The Swiss federal statistics office says the number of assisted suicides has been growing fast: Nine years ago, there were 297. By 2015, the most recent year tabulated, the figure had more than tripled to 965. Nearly 15 percent of the cases last year were people under 65 years old.