The health of Singapore's first prime minister, Lee Kuan Yew, who has been in hospital with pneumonia since February 5, has worsened, the government said on Tuesday.

The Prime Minister's Office said that Lee, 91, who is on a ventilator in the intensive care unit of Singapore General Hospital, had an infection and was being treated with antibiotics.

Born in 1923, he co-founded the city state in 1965 when it declared its independence from Malaysia and was its prime minister for more than three decades.

Lee was succeeded as prime minister by Goh Chok Tong in 1990, before Lee Kuan Yew's son Lee Hsien Loong took power in August 2004.

The elder Lee has been credited with Singapore's remarkable transformation from a colonial trading post to a prosperous financial center.

However, he has also been a divisive figure, attracting criticism for stifling media freedom and for the harsh treatment of political opponents.