(ShareCast News) - Trading firm IG Group posted an increase in revenue in the first three months of the year, although it warned market volatility had made it harder to predict an outcome for the full year.In the quarter to the end of August, revenue rose 24% year-on-year to £106m, driven higher by growth in all regions, although an increase in numbers in Europe was partially offset by a decline in average revenue per user.Meanwhile, client numbers rose 19% from the corresponding period in 2014 and 4.9% quarter-on-quarter, despite the quarter being a normally very quiet period for firms operating in the business and financial markets sector.The FTSE 250 group said it has made a strong start to the year, although it sounded a cautious note indicating that it was too early to predict how the markets will react this year.IG shares were up 4.02% to 764.00p at 0836 BST on Tuesday.