Billionaire Carlos Slim Helu has increased his stakes in newspaper company New York Times Co and luxury retailer Saks Inc.

Through the fund Inmobiliaria Carso S A, Slim bought 553,000 Class A shares of New York Times on August 18 at prices ranging from $6.83 to $7.09 per share, according a regulatory filing.

The purchases increased Slim's stake in the company, which publishes its namesake newspaper as well as the Boston Globe, to 7.3 percent from 6.9 percent.

Slim, Saks' largest shareholder, bought 620,000 Sakes shares on August 18, giving him a total of 26.24 million, or a 16 percent stake in the upscale department store chain's shares. In early 2010 he held 25.62 million Saks shares.

Shares of New York Times and Saks rose about 4 percent on Tuesday.

Slim, with a fortune estimated at about $74 billion, was named the world's richest man by Forbes magazine in March for the second year running.

The 71-year-old Mexican tycoon has a reputation for having an eye for a bargain. He recently sold a stake he had accumulated in oil services company Bronco Drilling for a healthy profit.

New York Times repaid a $250 million loan to Slim on August 15, about five months earlier than expected.

Slim still holds warrants to buy 15.9 million Class A common shares of New York Times. The warrants expire on January 15, 2015.

Shares of New York Times are down nearly 36 percent this year.

Saks' shares are off 35.6 percent from 52-week highs hit in February on fears the stock market volatility and Wall Street layoffs could prompt luxury shoppers to pull back.

Saks last week forecast sales at its stores open a year or more would rise by a mid-to-high single-digit percentage in the second half of its fiscal year, which includes the holiday season. It said the current state of the stock market and the economy warranted caution in its planning.

(Reporting by Jennifer Saba and Phil Wahba in New York and Elinor Comlay in Mexico City; editing by John Wallace)