A human rights lawyer lodged a case yesterday with the International Criminal Court (ICC), calling President Rodrigo Duterte a "mass murderer" and seeking an investigation into "this dark, obscene, murderous and evil era in the Philippines".

In his 77-page complaint filed with ICC prosecutor Fatou Bensouda, Mr Jude Jose Sabio sought to have Mr Duterte and 11 others arrested and held in The Hague to prevent him "from further committing mass murder and from killing potential victims and witnesses".

Mr Sabio said Mr Duterte "has been repeatedly, unchangingly, and continuously committing extrajudicial executions or mass murders constituting a crime against humanity" since he was elected mayor of the southern city of Davao in 1988.

Some 1,400 people were killed by "death squads" when Mr Duterte was mayor of Davao, and at least 7,000 have died at the hands of police or state-backed vigilantes since he became President last June, Mr Sabio alleged.

He offered as evidence testimonies provided to the Senate by two self-confessed assassins who claimed to have been part of Mr Duterte's "death squads" - Mr Edgar Matobato and Mr Arthur Lascanas. Mr Sabio is Mr Matobato's lawyer.

Some 1,400 people were killed by "death squads" when Mr Duterte was mayor of Davao, and at least 7,000 have died at the hands of police or state-backed vigilantes since he became president last June, Mr Sabio alleged.

Mr Matobato, 57, said he and a militia of six other men began killing in 1988.

They disembowelled their "marks", or torched them, or fed them alive to crocodiles.

By the mid-1990s, their small band grew to squads of more than 500. When he walked away from it all in 2013, he said, he would probably have taken part in more than 1,000 murders.

Mr Matobato said the goal was to strike fear into the hearts of criminals and chase them out of Davao city. He said Mr Duterte gave the orders to kill.

He said he personally saw Mr Duterte unload two magazine clips of an Uzi on a government agent that his men had a run-in with.

Mr Matobato also tagged Mr Lascanas, 56, a policeman at the time, in some of these murders, describing him as a "handler" of assassins, and someone "very close" to Mr Duterte.

Mr Lascanas rebuffed Mr Matobato's allegations during an initial appearance before the Senate. But he later walked back on his testimony, and corroborated much of what Mr Matobato said.

Mr Duterte's aides have dismissed these allegations as "fabrications".