JOHANNESBURG (Reuters) - The International Monetary Fund (IMF) said on Monday it expected Namibia's economy to grow by five percent this year, lower than the 5.7 percent forecast by the southern African nation's government. The IMF said in a statement after a team led a mission to Namibia that growth would be supported by mining production and the construction sector, but added that "growth prospects are increasingly clouded with downside risks." Risks included "highly volatile Southern African Customs Union (SACU) revenues," the IMF said. (Reporting by Ed Stoddard; Editing by Stella Mapenzauswa)