TOKYO, July 1 (Reuters) - Japan's economy shrank more than expected in the first quarter, the government said in a rare unscheduled revision to gross domestic product (GDP) data on Monday, darkening prospects for a fragile recovery.

Japan's real GDP shrank an annualised 2.9% in January-March, down from an earlier estimate of a 1.8% contraction, the revised data showed.

The real GDP for the October-December period was also revised down to an annualised 0.1% growth versus the previous 0.4% increase, while that for the July-September period was revised down to an annualised 4.0% decline from the previous 3.7% drop. (Reporting by Yoshifumi Takemoto, writing by Leika Kihara Editing by Chang-Ran Kim)