SINGAPORE - Prime Minister Lee Hsien Loong has penned a congratulatory letter to his newly appointed Malaysian counterpart, Prime Minister Muhyiddin Yassin.

In the letter, he reaffirmed the "deep, long-standing relationship" between both countries and reiterated an invitation for Mr Tan Sri Muhyiddin to make an official visit to Singapore at his earliest convenience.

"We are connected by history, geography and close bonds of friendship and kinship," Mr Lee wrote. "Over the years, Singapore has cooperated with successive Malaysian governments in a wide range of areas, for mutual benefit."

He added that Mr Muhyiddin would be familiar with many of these projects from his previous appointments in the Federal Government as well as Menteri Besar of Johor.

"I am confident that our bilateral relationship will continue to thrive and flourish under your leadership as Prime Minister of Malaysia," Mr Lee wrote.

On Sunday, PM Lee had called Mr Muhyiddin - president of the Parti Pribumi Bersatu Malaysia - to congratulate him and invite him to Singapore for a visit.

"I appreciate having the chance to speak to you on the phone yesterday, amidst your many urgent preoccupations," Mr Lee said.

He added: "There are many areas our two countries can move forward on together, in the current challenging external environment."

PM Lee also said that he and his wife, Ms Ho Ching, send their best wishes for Mr Muhyiddin's good health and happiness, and look forward to meeting him and his wife, Puan Sri Datin Noorainee, soon.