More problems for the world's biggest bank with raids on the Seoul office of Citigroup Global Markets, according to news reports out of South Korea.

Prosecutors say they are investigating the involvement of Ciitgroup Global Markets in Lone Star Funds' takeover of Korea Exchange Bank (KEB) in 2003 and whether there was any stock price manipulation of KEB's credit card division in 2003 after Lone Star purchased KEB.

Citigroup Global Market Securities, formerly known as salomon smith barney, was a financial advisor to KEB when it merged with the credit card unit.

The Citigroup behemoth seems to be going from mini-crisis to another around the world. None of them earth-shattering, but not a good look either.

Earlier this year in Japan, Citigroup got into trouble with regulators over a computer glitch that mucked up around 275,000 transactions. I explored that incident in this blog entry here.

Meanwhile in Australia, Citigroup is being sued by the regulator for insider trading and conflicts of interest. I talked about that issue on Australian ABC radio presented via this blog entry here.

All this does raise the question whether we are seeing a pattern of an outfit that just might be too big.