KIEV, June 1 - Moody's Investors Service has downgraded Naftogaz Ukrayiny's foreign currency corporate family rating, probability of default and debt ratings from B2 to Caa1.

The outlook on the ratings was changed to negative.

Moody's said it had now concluded the review of Naftogaz's ratings started by the agency on March 11.

According to the statement, the rating action reflects Moody's reassessment of the company's fundamental credit quality, as expressed by its Baseline Credit Assessment (BCA) as well as the government support factor, which plays an important role in the overall rating of Naftogaz.