Citigroup, America's biggest financial services company, announced a 13% jump in operating income during the second quarter, buoyed by growth at its international consumer arm.

The New York-based company, which runs banking, insurance and brokerage operations in around 100 countries, earned $3.8bn (�2.7bn) in the quarter, compared with $3.3bn during the first three months of the year.

While the slowing US economy and stock market slump left many of its competitors with unpaid debt and losses on investments, Citigroup said its international branch network was the main source of growth.

Citigroup's smaller rival, Bank of America, unveiled second-quarter net income down 2% year on year, owing to loan losses and slack trading results.

"The strength and diversity of our global franchises produced results that once again proved Citigroup's ability to increase revenue and earnings, even in light of the difficult market conditions," Citigroup chairman and chief executive Sandy Weill said in a statement.

Citigroup also said its global corporate division, which includes its investment and corporate banking businesses, posted a 10% rise in profits to $1.7bn.

Citigroup's stock, which closed at $48.86 on Friday, was up more than $1 in pre-market trade on Monday.