Mr Morrison said that on behalf of the people of Australia he would like to thank Mr Abe for his enduring commitment to Australia-Japan relations over his long and successful career.

"Shinzo Abe is a true friend. He is Australia's true friend," Mr Morrison said in a statement on Friday night.

Mr Abe, 65, announced earlier on Friday he would step down.

He has battled the disease ulcerative colitis for years and recent hospital visits fanned speculation as to whether he could stay in the job until the end of his term in September 2021.

On Monday, Mr Abe surpassed a record for longest consecutive tenure as Japanese premier, having returned as prime minister in December 2012.

Mr Morrison said Japan was one of Australia's closest partners, "propelled by Prime Minister Abe's personal leadership and vision, including elevating the relationship to new heights under our Special Strategic Partnership".

He said the political stability Mr Abe had delivered over eight years had been a major asset for Japan.

Mr Morrison said one of the most moving experiences he had had as prime minister was to lay a wreath with Mr Abe at the Cenotaph in Darwin.

"Standing side by side, we honoured Australia's fallen and marked the bonds of loyalty and friendship that our two countries now share."

Mr Morrison said Australia and Japan shared a vision for an open, peaceful and prosperous Indo-Pacific region.

"Prime Minister Abe is a man of integrity and wisdom. He has been the senior statesman in our region and across the globe, a strong promoter of open trade and an outstanding international diplomat for Japan.

"I wish Prime Minister Abe all the best for his health. I look forward to continuing our friendship, and Jenny and I wish he and Akie the very best for the future."

Australian Associated Press