Lauren Parker has won Australia's 10th silver medal at the Tokyo Paralympics, in a dramatic finish to the women's PTWC triathlon on day five.

Parker led from the opening swim leg of the triathlon at the Odaiba Marine Park, and she maintained the lead through every transition and the bike and run legs.

But as she began to tire in the final section of the race, Kendall Gretsch of the United States was coming with a fast-finishing burst.

Parker still led around the final corner, but in the finishing straight Gretsch was gaining ground with every turn of the wheel.

She drew level with only metres to go, and rolled clear to cross the line less than a bike length in front for the gold.

Parker, from Chisholm in New South Wales, said after the race she had given it everything in the final stages.

"But I got stuck at one of the U-turns (on the course) behind someone on that last lap, which was unfortunate.

"That was a few seconds that I lost, but I put in everything that I could.

"I just put my head down and went for it … I'm happy with the effort I put in and, yeah, I'm proud of my effort."

Four years ago, Parker was involved in a cycling accident while she was training. Both tyres on her bike burst at high speed and threw her into a guard rail.

She suffered a spinal cord injury and several other injuries.

"I wouldn't be here without my best friend and training partner, Brad Fearnley, and he's been with me for 14 years, helping me with my career," she told Channel Seven.

"He's stuck by me ever since I've had my accident. Every single day, every single training session he's been there.

"I wouldn't be here, racing for my country at the Paralympic Games in Tokyo, without him.

"Four years ago, I was lying in a hospital bed thinking that my life was over, and I had amazing support around me, and if it wasn't for that support I wouldn't have overcome that life-changing injury

"I've overcome many surgeries and many obstacles over the last four years, but I never would have dreamed of representing my country four years later."

Parker said she would head to the United States next week for more competition, then into training for next year's para-triathlon world titles, and beyond.

Australia won two more medals in athletics.

Robyn Lambird took bronze in the women's 100m T34 event, behind British Paralympic great Hannah Cockroft.

Lambird finished in a season's best 18.68 seconds, as Cockroft broke the world record in a time of 16.39.

Sarah Edmiston also won a bronze medal in the women's discus F64.

Edmiston was in the bronze medal position going into the final round with a throw of 36.83m, before confirming her spot on the podium with a final-round throw of 37.85.

The Chinese pair of Juan Yao and Yue Yang won gold and silver respectively.