LOS ANGELES (Reuters) - Harrah's Entertainment Inc. (HET) said on Monday it has closed its $6.8 billion purchase of rival Caesars Entertainment (CZR), creating the world's largest casino operator.

The combined company has nearly 100,000 employees and $9 billion in annual revenue from 40 properties, including riverboats and hotel-casinos in 12 states and three countries.

Harrah's offer, which included $1.9 billion in cash and $4.9 billion in Harrah's shares, was first announced last July.

The deal was approved last week by the Federal Trade Commission and gaming regulators in Nevada, following earlier approval by regulators in New Jersey, Louisiana, Mississippi and Indiana.

In the key Las Vegas market, Harrah's now controls 6 properties, compared with the 10 resorts owned by No. 2 gambling company MGM Mirage (MGM), which in April acquired Mandalay Resort Group.

Harrah's describes its casino portfolio as "the most diverse in the gaming industry."

Caesars' shares closed Monday's session on the New York Stock Exchange down $3.81, or nearly 18 percent, at $17.73, while shares of Harrah's rose $1.35, or nearly 2 percent, to $73.17.