UPDATE 1-Mexican Slim's brokerage buys Citigroup shares

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MEXICO CITY, Nov 25 (Reuters) - A Mexican brokerage controlled by billionaire Carlos Slim, has recently bought $150 million worth of shares in U.S. bank Citigroup (C.N).

The brokerage arm of Slim's Inbursa (GFINBURO.MX) financial group bought almost 29 million of Citigroup's Mexico City-traded shares (C.MX) from Nov. 19 to Nov. 25, according to Reuters data on Tuesday.

It was unclear whether Inbursa was buying the shares for Slim. A spokesman for Slim said Inbursa bought the stock on behalf of its "investment funds and clients".

Shares of Citigroup have surged close to 60 percent this week after the U.S. government agreed to shoulder most losses on about $306 billion of the bank's risky assets and inject new capital.

Citigroup's stock plummeted last week to its lowest level since December 1992, raising doubts about the bank's ability to survive.

"Ever since the stock began to come down they've been pretty active buying blocks through Inbursa. Who knows who the buyer is, but it's interesting," one analyst said.

Referring to Slim, the analyst said: "He in the past has been an opportunity buyer of distressed shares. This is very much in his style."

Analysts say Citigroup could decide to sell its Banamex bank in Mexico to raise capital for its U.S. operation. If Banamex, Mexico's No. 2 bank, goes on the block, Slim would be the most obvious buyer, they say.

Slim's spokesman said last week the mogul was not currently interested in Banamex, bought by Citi in 2001 for $12.5 billion, a record acquisition at the time for Mexico.

($1 = 13.23 pesos) (Reporting by Noel Randewich and Armando Tovar; Editing by Gary Hill)