LONDON, April 18 (Reuters) - Nickel clocked its largest one-day gain since the financial crisis on Wednesday as what analysts said were misplaced concerns that the metal would become ensnared in U.S. sanctions on Russian companies caused it to break through key technical levels.

Three-month nickel on the London Metal Exchange soared around 12 percent to a more than three-year high of $15,875, before trading up 5.2 percent at $14,950 a tonne at 1433 GMT.