NATO's chief said the alliance sees no need to change its nuclear weapons alert level, despite Russian officials upping their threats of escalation, days after raising the specter of a nuclear attack.

The alliance's Secretary-General Jens Stoltenberg, spoke to The Associated Press following talks on European security.

Stoltenberg said, "We will always do what is needed to protect and defend our allies, but we don't think there is any need now to change the alert levels of NATO's nuclear forces,"

Stoltenberg's comments come after the Kremlin reported on Monday that its land, air and sea nuclear forces were on high alert following an order by Russian President Vladimir Putin over the weekend.

NATO itself has no nuclear weapons, but three of its members, the United States, Britain and France, do.