* U.S. inventories rose by 4.3 mln barrels last week - API
* IMF cuts euro zone growth forecasts
* Iran starts injecting uranium gas into centrifuges (Updates prices)
LONDON/SEOUL, Nov 6 (Reuters) - Oil prices fell on Wednesday after a larger-than-expected build in U.S. crude inventories and weak euro zone economic figures, reversing some of the gains of the previous three sessions.
Brent crude was down 32 cents at $62.64 a barrel by 1439 GMT. West Texas Intermediate crude was down 7 cents at $57.16 per barrel.
The slide followed figures from the American Petroleum Institute (API) showing U.S. crude inventories rose by 4.3 million barrels in the week ended Nov. 1 to 440.5 million barrels. Analysts forecast a rise of just 1.5 million barrels.
Official data from the U.S. government's Energy Information Administration (EIA) is due later on Wednesday.
"Market participants will closely monitor if the build is confirmed by the EIA later today, considering that last week API had a crude draw and the EIA a crude build," said Giovanni Staunovo, oil analyst for UBS.
The International Monetary Fund (IMF) said euro zone economic growth was set to slow more than expected as the bloc's manufacturing crisis could spill over to the larger services sector under global trade tensions.
Data on Wednesday showed Germany's services sector barely grew in October, while euro zone business activity expanded slightly faster than expected last month but remained close to stagnation.
Middle East tensions offered some support, as Iran started to inject uranium gas into centrifuges at an underground nuclear facility, further distancing itself from a 2015 nuclear deal between Tehran and world powers.
The United States pulled out of the nuclear pact last year and has imposed tough new sanctions on Iran.
"Alongside the continued rolling back of its nuclear commitments, the OPEC nation may be tempted to cause further supply disruptions in the Middle East in a bid to drive up prices," PVM analyst Stephen Brennock said.
"Accordingly, conditions are ripe for tensions in the region to escalate and for the geopolitical risk premium to strike back with a vengeance."
However, Russian Energy Minister Alexander Novak said the current oil price of more than $60 per barrel showed that markets were stable.
(Reporting by Bozorgmehr Sharafedin in London and Jane Chung in Seoul; Editing by Louise Heavens and Edmund Blair)