A Boeing 737 has crashed on landing in the Russian city of Kazan, with all 50 people on-board feared dead, the emergency ministry has told Reuters.
More top news
The country's top defence officer said the force may ignore any order to launch a nuclear attack which is deemed to be illegal.
Navy officials say they have received seven short satellite calls which are though to have come from the submarine.
The President's normally slavish sycophants are expected to remove him as party leader ahead of new exit talks with the army.