TOKYO (REUTERS, AFP) - Japanese Prime Minister Shinzo Abe, the nation's longest-serving premier, said on Friday (Aug 28) that he is resigning due to health reasons.

Here is what some international leaders and businessmen are saying:

Singapore Prime Minister Lee Hsien Loong

"I am sorry to learn that Japanese Prime Minister Abe Shinzo has resigned from office for health reasons.

"I have worked well with Mr Abe for close to nine years. Under his leadership, our bilateral relations have deepened. We last met in person in November, and more recently online in April, during the virtual Asean Plus Three Summit on Covid-19.

"Mr Abe also played a critical role in concluding the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) after the US left the original Trans-Pacific Partnership negotiations.

"I wish Abe-san a good recovery as he begins treatment for his condition."

British Prime Minister Boris Johnson

"@AbeShinzo has achieved great things as PM of Japan - for his country and the world," Johnson said on Twitter.

"Under his stewardship the UK-Japan relationship has gone from strength to strength in trade, defence and our cultural links. Thank you for all your years of service and I wish you good health."

US President Donald Trump

"I want to pay my highest respect to Prime Minister Shinzo Abe... a great friend of mine," Trump told reporters on Air Force One.

"I just feel very badly about it."

Trump said Abe loved his country very much, adding that he planned to call the Japanese leader.

South Korea's presidential Blue House spokesman Kang Min-seok

"We regret the sudden resignation announcement by Prime Minister Abe, who has long played many roles for the development of South Korea-Japan relations."

"The South Korean government will continue cooperation with the new Japanese prime minister to promote friendly bilateral ties."

China's foreign ministry spokesman Zhao Lijian

"This is an internal affair of Japan and we will not comment. China and Japan are close neighbours, and China is willing to work with Japan to continue to promote the development of China-Japan relations."

Australian Prime Minister Scott Morrison

"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. He has advocated for the region's prosperity and stability, bringing his leadership as an experienced statesman of the first order.

"Prime Minister Abe steps down as a regional leader having made unprecedented contributions, particularly as we respond to the health and economic impacts of Covid-19."

Taiwan President Tsai Ing-wen

"Prime Minister Abe was always friendly to Taiwan, whether on policy or the rights and interests of Taiwan's people - he was extremely positive. We value his friendly feelings towards Taiwan and hope he is healthy."

Mr Kwon Tae-shin, vice-chairman of the Federation of Korean Industries, a South Korean business lobby group

"President Moon Jae-in and Abe do not have good personal relationship, which contributed to adverse bilateral ties. When a new leader takes office in Japan, he can give momentum to improving bilateral relations.

"The two countries acknowledge that unnecessary diplomatic and trade conflicts would not help each other at a time when Covid -19 further adds difficulty to trade and business activities globally."

Mr Marcus Schurmann, chief executive of the German Chamber of Commerce and Industry in Japan

"He did a lot of good with regard just to the fact that he was one of the key promoters for multilateralism and free trade and did a lot to move to Japan back onto the world stage. Japan recovered the visibility and recognition the third-largest economy in the world deserves.

"We have FTAs (free trade agreements) and he also tackled a lot of difficult problems; just thinking about relations with China, relations also with Russia, and also the difficult relationship with the US at least since Trump came into power.

"I do not want to say he failed, but at least what is an unsolved problem is the relationship with Korea. I think that's the kind of problem which his successor has to work on.

"He succeeded in bringing the Olympics to Tokyo. I think this is also a major achievement we should not forget."

German Chancellor Angela Merkel

Dr Merkal said she "regrets" the resignation of Mr Abe, hailing his "fight for multilateralism".

Dr Merkel said she and her fellow veteran leader in the Group of Seven industrialised nations had a "shared foundation of values".

"I of course regret his resignation and wish him all the best for his health," she told reporters. "We always worked very, very well together... He was always someone who committed himself to the fight for multilateralism."

Russian President Vladimir Putin's spokesman Dmitry Peskov

"Shinzo Abe really made an invaluable contribution to the development of bilateral Russian-Japanese relations."

"Of course, we wish Shinzo Abe a speedy recovery from all the health problems he mentioned."

Indian Prime Minister Narendra Modi

"Pained to hear about your ill health, my dear friend @AbeShinzo. In recent years, with your wise leadership and personal commitment, the India-Japan partnership has become deeper and stronger than ever before. I wish and pray for your speedy recovery."

International Olympic Committee President Thomas Bach

"It is with great sadness that I learned about the resignation of Prime Minister Abe.

"First of all, I would like to wish him all the very best in his fight against this disease with all the strength we know him to have. At the same time, I would like to thank Prime Minister Abe for his great leadership in getting the Olympic Games back to Japan after the Olympic Games Tokyo 1964, and in overseeing and supporting the overall preparation of these Olympic Games Tokyo 2020.

"His engagement was crucial to making the Tokyo Organising Committee the best prepared ever. Throughout these years, Prime Minister Abe was a strong partner who always stood up for the interests of Japan, and who at the same time could always be trusted. In this way, we were able to find solutions, even in the most difficult circumstances of the Covid-19 pandemic, which allow his vision for Japan to still come true, even if with one year's delay.

"All the Japanese athletes and the athletes of the entire world are very grateful to him."

Indonesian President Joko Widodo

"PM Abe was one of the first world leaders I met when I took office as President of Indonesia in 2014. Under his leadership, we witness stronger bilateral relations between Indonesia-Japan.

Thank you PM @AbeShinzo @JPN_PMO for your friendship. Wishing you good health always."