Letter claiming responsibility for Dortmund attack is unusual - official

DUESSELDORF, Germany, April 12 (Reuters) - The interior minister of the German state of North Rhine-Westphalia described as "unusual" a letter claiming responsibility for Tuesday's attack on a bus carrying players from soccer club Borussia Dortmund. Ralf Jaeger told reporters that police in North Rhine-Westphalia had again taken additional security measures in Dortmund, where Borussia and AS Monaco will face off for their postponed Champions League clash on Wednesday evening. (Reporting by Anneli Palmen; Writing by Paul Carrel; Editing by Joseph Nasr)