Maariv newspaper, citing medical sources, reported on Thursday that the cardiologists stabilised Sharon's condition on Wednesday but found that he suffered from a heart murmur that may allow blood clots to filter to the brain where they may cause additional strokes.

Ron Kromer, a spokesman for the Hadassah hospital in Jerusalem where the prime minister is being treated after suffering a severe stroke a week ago, said Sharon's heart rate was normal when asked about the report on Thursday, but he did not comment directly on the newspaper account.

"The prime minister's condition continues to be critical but stable," he said. "He will undergo a [brain] scan later in the day."

Sharon, 77, had been due to undergo a heart cathertisation procedure to close a congenital hole in the heart. But he suffered a severe stroke on 4 January on the eve of the operation and has been critically ill in hospital since then.