The identities of the persons of interest linked to the individual whom Vice President Sara Duterte allegedly contracted to assassinate top government officials cannot be disclosed, National Bureau of Investigation (NBI) Director Melvin Matibag said.

Matibag made the statement while testifying before the Senate impeachment court on Tuesday, 21 July.

Aside from revealing that the NBI's investigation had identified persons of interest related to the alleged "hitman," Matibag said a Special Task Force had been created to investigate what the bureau considers "serious, active, and continuing threats" against the President.

Matibag said the task force was established to help safeguard the President from any possible assassination attempt.

“The mandate of the Special Task Force is clear, and its mandate is to continue guarding the security of the President and to find and identify who the Vice President contracted to kill the President,” he said.

House prosecutor Rep. Gerville Luistro asked Matibag whether the NBI had identified the alleged hitman.

Matibag replied that investigators had developed leads on the potential assassin but declined to disclose details, stressing that the investigation remains active and ongoing.

“Respectfully, Mr. Presiding Officer, it saddens me, but in my capacity as NBI director, I cannot disclose the identities of our persons of interest because, like I said, this is a continuing and open investigation regarding the contracting of an assassin to kill the President,” he told the court.

Luistro argued that the public, as well as the senator-judges, had long been waiting to know the identity of the person whom the Vice President allegedly contacted.

Despite Luistro's insistence, Matibag stood firm, saying he did not want to compromise the investigation or betray the trust of the bureau's sources.

He added that the disclosure of persons of interest is restricted by law.

“It will violate the right to privacy of the individuals that we tagged as persons of interest, which is punishable under the Administrative Code... It is an exemption under the Freedom of Information,” he said.

Matibag is expected to return to the witness stand after the defense requested additional time to continue its cross-examination.

The NBI chief had earlier been identified as the prosecution's final witness on Article IV of the Articles of Impeachment, which deals with the alleged grave threats made by Duterte.