A former senior KGB officer who met a Russia intelligence expert just hours before his shooting in the US, on Sunday expressed doubt that the incident was related to the case of Alexander Litvinenko, a former KGB officer poisoned last year in London.

The Federal Bureau of Investigation is assisting a police inquiry into the shooting on Thursday of Paul Joyal, a former Senate intelligence committee security director and editor of a newsletter on Russia. Mr Joyal recently accused the Kremlin on US national television of involvement in the Litvinenko death.