Story highlights Lascanas says he killed his own brothers out of "loyalty" to Duterte

Duterte's office says the president has already been cleared multiple times

(CNN) The self-confessed leader of the Davao Death Squad accused Philippines President Rodrigo Duterte of ordering mosque bombings and the murder of a journalist during his time as Davao mayor.

In a news briefing Monday morning, retired policeman Arturo Lascanas backed up 2016 allegations made by former hitman Edgar Matobato, including claims of a 300-member execution squad run out of the southern city of Davao.

"I was one of those who started it," he said. "We implemented the personal instructions of (then-Mayor) Duterte to us. All of the killings we did in Davao city, whether we buried or threw them out to sea."

Retired police officer Arturo Lascanas speaks during a news conference at the Philippine Senate in suburban Pasay, south of Manila, on Monday, February 20.

Duterte, though a spokesman, dismissed the allegations as "nothing but vicious politics."

"The Commission of Human Rights, the Office of the Ombudsman, the Senate Committee on Justice already cleared the President of extrajudicial killing and his involvement in the Davao Death Squad," presidential communications secretary Martin Andanar said in a statement.