De Lima: I guarantee fair, professional inquiry

Metro Manila (CNN Philippines) — Amid her word war with President Rodrigo Duterte, Sen. Leila De Lima said the Senate probe into the extrajudicial killings unleashed by the administration's campaign on illegal drugs will remain fair and will be conducted "in the most professional manner."

De Lima, who is the chairman of the Committee on Justice and Human Rights, will lead the two-day Senate joint committee hearing on Monday, along with Sen. Ping Lacson, who chairs the Committee on Public Order and Dangerous Drugs.

In an exclusive interview with CNN Philippines, De Lima claimed the rising number of extrajudicial killings, involving alleged drug personalities, is a "very important issue of public interest," saying that even the international community has taken notice of "this phenomenon of summary executions."

"There is no denying the fact that this is a very important issue of public interest and national importance, and this is something bigger than Sen. Leila De Lima," she said. 

Earlier, De Lima filed a resolution to dig deeper into these extra-judicial killings in relation to the war on illegal drugs. With the rising figure of supposed drug-related deaths, the Senator said she wants to know how many really are legitimate police operations and how many are committed by the vigilantes.

President Rodrigo Duterte claimed that De Lima's supposed romantic affair with her former driver and bodyguard, Ronnie Dayan, "gave rise" to corruption at the New Bilibid Prison (NBP).

Related: De Lima on Duterte's claims: Bits of truth — but mostly lies

Related: De Lima to Duterte: Show some decency

Although De Lima admitted having "close relationship" with Dayan, the senator denied her involvement with the illegal drug trade.

Law enforcement officials are expected to attend the investigation, including PNP Chief Ronald Dela Rosa, and key officials from the Philippine Drug Enforcement Agency (PDEA) and the National Bureau of Investigation (NBI).

WATCH: Duterte fires back at De Lima

Interior Sec. Ismael Sueno and officials from the Commission on Human Rights (CHR) are also expected at the hearing.

Families of the victims of summary executions will also be presented during the inquiry.

CNN Philippines Correspondent Cecille Lardizabal and Digital Producer Arra Perez contributed to this report.