(Reuters) - Billionaire investor Carl Icahn has raised his stake in Occidental Corp <OXY.N> to nearly 10% from 2.53% at the end of last year and once again pushed for an overhaul of the oil and gas producer's board, an SEC filing http://bit.ly/2Qb9byt on Thursday showed.

Icahn bought about 88.6 million shares for $2.21 billion as Occidental's shares plummeted to two-decade lows due to a slump in oil prices.

This is in contrast to his move in February when he disclosed that he cut his stake to 22.6 million shares, or 2.53%, as of Dec. 31.

The activist investor has been waging a bitter battle with Occidental's board over its $38 billion acquisition of Anadarko Petroleum, calling it a misplaced bet based on expectations of higher oil prices.

"It is one of the worst disasters in financial history and we believe the CEO and Board must be held accountable, and the Board must be replaced," Icahn said in the filing.

Occidental's market value had fallen to $12 billion on Monday, less than a third of what it paid for Anadarko and its debt ballooned to about $40 billion.

Icahn expects strong bids to emerge for Occidental once the U.S. West Texas Intermediate crude price recover in the near-to-medium term, according to the filing.

Following the slump in oil prices, the company had slashed its dividend and unveiled fresh spending cuts.

(Reporting by Shanti S Nair in Bengaluru; Editing by Arun Koyyur)