"His state of health is stable and unchanged" since Friday, Sheba Medical Centre spokeswoman Orly Levy told AFP.
The hospital announced on Friday that Sharon had been transferred from the
department of respiratory rehabilitation to its intensive care unit "due to a weakening of his condition".
"Sharon contracted an infection that is affecting his heart and will receive intensive treatment to combat the infection," the statement said.
The former statesman, who oversaw Israel's withdrawal from the Gaza Strip in 2005 following a 38-year occupation of the Palestinian territory, dramatically disappeared from public life after suffering a massive stroke in January.
Friday's statement was the first public update on the 78-year-old Sharon's health since August, when he had another spell in intensive care after coming down with pneumonia and kidney problems.
Sharon, who was elected premier in early 2001, suffered a massive brain haemorrhage on January 4 and was moved from a Jerusalem hospital in May to Tel Hashomer, a facility on the outskirts of Tel Aviv, for long-term treatment.
His stroke signalled a dramatic end to the career of the former general who had been on course at the time for re-election as head of the brand new Kadima party he created just two months before collapsing.
Sharon was succeeded by his close ally Ehud Olmert, who led Kadima to a less than convincing victory in a March election.

Copyright AFP (Agence France-Presse), 2006