LONDON, July 22. /ITAR-TASS/. Fitch Ratings has upgraded Russian mining and metals giant Norilsk Nickel's Long-term Issuer Default Rating (IDR) to BBB-from BB+, with a stable outlook, the international rating agency said on Tuesday.

Fitch also raised Norilsk Nickel’s short-term foreign currency IDR to F3 from B and senior unsecured foreign currency rating to BBB-from BB+.

The upgrade reflects an improvement in the company’s corporate governance after Norilsk Nickel’s main shareholders - aluminum giant RusAl and Interros holding company - signed a shareholder agreement in December 2012 with the mediation of Millhouse, a company affiliated with Russian tycoon Roman Abramovich and introduced as Norilsk Nickel’s new shareholder, the agency said in a statement.

“The shareholder agreement is designed to improve the corporate governance and transparency of Norilsk Nickel, to maximize profitability and shareholder value and to settle all disagreements between Interros and RusAl in relation to the company,” Fitch said in a statement.

Norilsk Nickel is a diversified mining and metallurgical company, the world’s largest producer of nickel and palladium, and a leading producer of platinum, cobalt, copper and rhodium. The company also produces gold, silver, iridium, osmium, selenium, ruthenium and tellurium.

• [Editor:Juan]