The Standard & Poor's (S & P) ratings agency has cut the credit ratings of state-controlled Russian energy companies Rosneft and Gazprom to BBB- from BBB.
The April 28 S & P announcement downgrading the Russian companies a notch above junk rating followed an earlier announcement from the United States that it was imposing new sanctions on Russian officials, including Rosneft CEO Igor Sechin.
Rosneft shares dropped more than 1 percent on the news.
Sechin later dismissed the U.S. sanctions against him saying it would not harm his company's cooperation with foreign partners, including with U.S. companies.
British energy group BP said on April 28 it remained committed to its investment in Rosneft despite the sanctions.
The sanctions apply only to Sechin but analysts said the measures could hinder Rosneft's activities.
Based on reporting by Reuters and Interfax