Investor Warren Buffett's Berkshire Hathaway Inc sold 2.9 percent of its holdings in debt ratings agency Moody's Corp this week, raising $28.7 million in the transaction, according to a regulatory filing on Friday.

The move follows another reduction in Berkshire Hathaway's stake in Moody's in July, when it cut its stake to 16.98 percent from 20.4 percent.

Omaha, Nebraska-based Berkshire sold 1.15 million shares, leaving it with with 38.07 million, according to the filing, still making it Moody's largest shareholder by far.

Moody's and its main rival McGraw-Hill Cos' Standard & Poor's were hit hard by a slump in debt issuance during the recession.

Moody's and other ratings agencies came under fire for assigning high ratings to mortgage-related securities that later defaulted.

(Reporting by Phil Wahba; Editing by Nick Macfie)