The Philippine senator who led an investigation into the president's bloody anti-drug campaign has been ousted from the justice committee in a vote by the 24-member chamber that human rights advocates said could derail accountability in the crackdown.

Allies of President Rodrigo Duterte led the vote Monday that removed Sen. Leila de Lima from the Committee on Justice and Human Rights, which has spearheaded an inquiry into the widespread killings of drug suspects that have alarmed President Barack Obama, U.N. officials and human rights watchdogs. More than 3,000 drug suspects have died since June in the crackdown.

Human Rights Watch said de Lima's ouster shows the Senate has more interest in covering up allegations of state-sanctioned murder than in exposing them, and urged that de Lima be reinstated.