The International Criminal Court may have the jurisdiction to prosecute perpetrators of thousands of alleged extrajudicial killings in the Philippines' crack down on drugs, a prosecutor at the Hague-based tribunal said.
Earlier on Thursday, Philippine President Rodrigo Duterte called U.S. President Barack Obama, the European Union and United Nations "fools" and said he would humiliate them if they questioned his war on drugs.
Nearly 2,300 people have died since Duterte started the campaign on June 30, according to police, of which 1,566 were drug suspects killed in police operations.
"I am deeply concerned about these alleged killings and the fact that public statements of high officials of the republic of the Philippines seem to condone such killings," ICC Prosecutor Fatou Bensouda said in statement.
The Philippines joined the ICC in November 2011 and extrajudicial killings could be prosecuted by the ICC if they are "committed as part of a widespread or systematic attack against a civilian population," she said.
The ICC, established under the 1998 Rome Statute, is a court of last resort. It only intervenes if a country is found to be unwilling or unable to prosecute crimes under its statute, including war crimes, crimes against humanity and genocide.