SAN SALVADOR, Feb 3 (Reuters) - Salvadoran presidential hopeful Nayib Bukele, a former mayor campaigning as an anti-corruption outsider, had 52.2 percent of votes with 24.7 percent of polling stations counted in Sunday's election, the electoral tribunal said. (Reporting by Nelson Renteria and Noe Torres, Writing by Daina Beth Solomon; Editing by Dan Flynn)