SINGAPORE -- Singapore's former prime minister Lee Kuan Yew has weakened further, the Prime Minister's Office (PMO) said on Sunday.

Concerns have been mounting over his health these days. Thousands of Singaporeans visited his hospital and a community center to leave flowers, gifts and emotional messages of support.

Prime Minister Lee Hsien Loong joined the well-wishers for his ailing father at the hospital on Sunday. He also visited Tanjong Pagar Community Club late Saturday to thank local residents for their prayers and support.

Lee, 91, was hospitalized in early February with severe pneumonia. In the past week his condition has worsened to critically ill and the government has given daily updates. The latest, on Sunday, said he had "weakened further."

Lee commands immense respect among Singaporeans, who this year will celebrate the country's 50th independence anniversary. He led Singapore for more than three decades until 1990, and is credited with transforming the resource poor island into a wealthy bustling financial hub with low crime and almost zero corruption.

At Singapore General where the elder statesman is hospitalized, 26-year-old university graduate Kim Lee fought back tears as she stood near the growing pile of flowers and cards.

"I came to give him my medal. I just finished a running event this morning and I came to give it to him," she said. "To me he is more than a champion."

Singaporeans overseas also sent in messages of support. Among the cards was one from the Netherlands, signed "a faraway Singapore son." Another message hailed the "countless extraordinary things" Lee did for the tropical city-state and wished for his recovery.

State media reported that about 1,000 people had gathered at a community center in Lee's electorate, also leaving cards and gifts and writing messages on a giant banner.

Lee co-founded the ruling People's Action Party and became the premier of the newly-born republic in 1965. After stepping down as prime minister in 1990, Lee remained part of the Cabinet and an influential figure in Singapore and the region.