Nigeria forecasts its economy will grow by at least 6.2 % in 2014.

(Reuters) - Nigeria forecasts its economy will grow by at least 6.2 percent this year following a solid first-quarter performance, the statistics office said on Tuesday.

That would be faster than growth last year, which was revised down to 5.5 percent last week.

Nigeria overtook South Africa as Africa's largest economy in April, after a rebasing of its calculation almost doubled its gross domestic product to more than $500 billion.

In the first quarter of 2014, the Nigerian economy also expanded by 6.2 percent from a year earlier, driven by its services sector, which offset a drop in oil production, the statistics office said on Tuesday.

"The first quarter is always the quarter with the slowest growth ... because it's the beginning of the planting season and consumers tend to spend less," Director General of the National Bureau of Statistics, Yemi Kale, told Reuters.

The first-quarter performance was slightly slower than a 6.8 percent annual expansion in the final three months of 2013.

The services sector, which accounts for half of GDP, expanded by 7.2 percent in January-March from a year earlier, decelerating from an 8.7 percent rise in the previous quarter.

Crude production fell to 2.26 million barrels a day in the first quarter, from 2.29 million barrels per day a year ago, due to pipeline shutdowns and oil theft.

Most governments overhaul GDP calculations every few years to reflect changes in output, but Nigeria had not done so since 1990, so sectors such as e-commerce, mobile phones and its prolific "Nollywood" film industry, had to be factored in. (Reporting by Chijioke Ohuocha; Editing by Susan Fenton)