The sudden death on Thursday of Saparmurat Niyazov, Turkmenistan’s autocratic and eccentric president, has raised the threat of instability in a Central Asian republic that is an important energy supplier to Europe.

Niyazov, known as Turkmenbashi or Ruler of the Turkmens, left the former Soviet republic he ruled for more than 20 years impoverished, internationally isolated and with no obvious successor. He died of a cardiac arrest, Turkmen state television reported. He was 66.