Singapore"s founding prime minister Lee Kuan Yew has died aged 91, only months before the island-republic he created celebrates its 50th anniversary of independence.

Singapore"s prime minister Lee Hsien Loong, Mr Lee"s son, confirmed the country"s founding father had died in a post on his Facebook page.

"The Prime Minister is deeply grieved to announce the passing of Mr Lee Kuan Yew, the founding prime minister of Singapore. Mr Lee passed away peacefully at the Singapore General Hospital today at 3.18am. He was 91," the post read.

The younger Mr Lee declared a period of national mourning from March 23 to 29 as Singaporeans awoke to news of his father"s death. A state funeral service will be held on March 29, followed by a private cremation.