NEW YORK (AFP) - The Dow jumped nearly 300 points Wednesday after the US Federal Reserve made no changes to its monetary policy, saying it can remain "patient" before moving to raise interest rates.

The Dow Jones Industrial Average gained 288.00 points (1.69 per cent) at 17,356.87.

The broad-based S&P 500 soared 40.15 (2.04 per cent) to 2,012.89, while the tech-rich Nasdaq Composite Index advanced 96.48 (2.12 per cent) to 4,644.31.

US stocks were in the green all day, but rose significantly after the Fed announcement in the early afternoon.

The S&P 500 roughly doubled its gains in the final two hours of trade.

In the statement, the Federal Open Market Committee (FOMC), the Fed's policy arm, left in place expectations that the central bank may raise interest rates only in the middle of 2015, downplaying speculation that a hike might come earlier than that because of the strength of the US economy.

Fed chair Janet Yellen, speaking at a news conference after the two-day FOMC meeting, that the US economy is "strengthening" but that decisions to raise rates remained data-dependent.

"There are no major surprises," said Art Hogan, chief market strategist at Wunderlich Securities. "But we have a statement that was perhaps less hawkish than expected, and then a succesful press conference" with Yellen.

Wednesday's gains snapped a three-day losing streak in US stocks amid concerns over the sharp fall in oil prices and a big drop in the Russian rouble.