(Adds reaction, background) YEREVAN, Jan 31 (Reuters) - An Armenian presidential candidate was wounded by unknown gunmen in the capital Yerevan on Thursday night, police said, in an attack that could delay February's election. Paruyr Hayrikyan, whose life was not in danger after the shooting, is one of eight candidates running in the Feb. 18 vote but is not seen as a strong challenger to Serzh Sarksyan, who is expected to be re-elected for a second five-year term.