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The US economy grew faster than previously estimated in the second quarter of the year, according to revised official figures.

The US Commerce Department said the economy expanded at an annualised pace of 3.9%, rather than 3.7%.

The growth in the economy overall was due to strong consumer spending, business investment and residential construction.

It rate is much higher than the 0.6% rate recorded in the first quarter.

The growth rate is expected to have slowed in the current quarter, but in a speech on Thursday Federal Reserve head Janet Yellen said economic growth appeared "solid" and the US remained "on track" for an interest rate rise this year.

The central bank head said as long as inflation was stable and the US economy was strong enough to boost jobs, the conditions would be right for a rise.

US interest rates have been held at near-zero since the 2008 financial crisis. When they finally do rise, it will be the first interest rate increase in nine years.

Jim Baird, chief investment officer for Plante Moran Financial Advisors, said: "Overall, the outlook on the US economy for the remainder of the year remains fairly optimistic, supported by continuing job creation, increasing consumer spending, improvements in the housing sector, and solid manufacturing numbers."

Stocks on Wall Street made a bright start in the wake of the GDP figures and Ms Yellen's comments, with the Dow Jones rising 1% in morning trade.