HSBC set aside $2 billion to cover U.S. law enforcement and regulatory costs and to compensate British customers for mis-selling as it reported a 3 percent dip in underlying profit.

A U.S. Senate report this month criticized HSBC for letting clients shift funds from dangerous and secretive countries, and HSBC said on Monday it was setting aside $700 million to cover "certain law enforcement and regulatory matters".

Analysts have said the issue could result in a fine of about $1 billion.

The Senate report criticized a "pervasively polluted" culture at the bank and said, between 2007 and 2008, HSBC's Mexican operations moved $7 billion into the bank's U.S. operations.

Chief Executive Stuart Gulliver on Monday apologized for the affair.

"We apologize for our past mistakes in relation to anti-money laundering controls, and it is a priority for senior management to build on steps already taken to manage risk and ensure compliance more effectively," he said.

Europe's biggest bank set aside $1.3 billion to compensate UK customers for mis-selling loan insurance and interest rate hedging products to small businesses.

HSBC on Monday reported a pre-tax profit of $12.7 billion for the six months to the end of June, up 11 percent on the year and above an average analyst forecast of $12.5 billion, according to a poll by the company. But underlying profit, stripping out gains from U.S. assets sales and losses on the value of its own debt, was down 3 percent on the year to $10.6 billion.

Shares in HSBC were down 0.1 percent to 530.8 pence, lagging a 1.2 percent rise in Europe's bank index.

Source: CNBC