Official results from the Philippines Election Commission shows key allies of detained former President Rodrigo Duterte and two liberal opposition candidates are among top winners in the nation's midterm Senate race.

Philippine governments have used extrajudicial killings and state terror to suppress working-class anger over declining living conditions and opposition to US-led war preparations against China.

Philippine President Ferdinand Marcos Jr has been dealt an unexpected blow in the midterms, with his Senate candidates set to pick up fewer seats than expected, according to early results. The election was a showdown between Marcos and his Vice-President Sara Duterte, daughter of former president Rodrigo Duterte.