Singapore's Minister Mentor Lee Kuan Yew meets with US President Barack Obama in the Oval Office of the White House in Washington, in this October 29, 2009 file photograph. [Photo/Agencies]

SINGAPORE - The health condition of Singapore's first prime minister Lee Kuan Yew, who has been in hospital with severe pnuemonia since Feb 5, has worsened, the government said on Tuesday.

"Lee Kuan Yew's condition has worsened due to an infection. He is on antibiotics. The doctors are closely monitoring his condition," the office of Prime Minister Lee Hsien Loong said in a statement.

Lee is being treated in a Singapore hospital where he has been placed ventilator.

The founding father of modern Singapore, Lee, who turned 91 last September, is widely credited with the city-state's economic success.

Although Lee has receded from the public and political scene, his health is watched closely as he is still seen as an influential figure for the current government, headed by his oldest son.

The Singapore dollar pared gains immediately after news of Lee's worsening health condition.

Lee, a Cambridge-educated lawyer, had a central role in building Singapore into one of the world's wealthiest nations on a per capita basis with a strong, pervasive role for the state and little patience for dissent.

Lee co-founded the People's Action Party, which has ruled Singapore since 1959 and led the newly born country when it was separated from Malaysia in 1965.

In a book published in 2013, Lee said he felt weaker by the day and that he wanted a quick death.

After Tuesday's news, the Facebook page of Singapore's prime minister was instantly flooded with hundreds of comments.

"For all his work and belief for and in us as a nation, we can only pray for his stability of health, and continue to carry on his profound legacy of building a better nation from all he has taught us," wrote Darius Lim.