MANILA -- The Philippines' security council will verify an alleged assassination threat by Vice President Sara Duterte against President Ferdinand Marcos Jr., a top official said on Sunday, describing it as a "matter of national security".

Duterte, in a strongly-worded morning briefing on Saturday, said she had spoken with an assassin and instructed them to kill Marcos, his wife and the speaker of the Philippine House if she were to be killed.

National Security Adviser Eduardo Ano said the government considers all threats to the president as "serious", vowing to closely work with law enforcement and intelligence communities to investigate the threat and possible perpetrators.

"Any and all threats against the life of the president shall be validated and considered a matter of national security," Ano said in a statement.

In response to Duterte's threat, Marcos' presidential security command said it had tightened its protocols in guarding the Philippine leader and the national police chief had ordered an investigation.

Duterte and Marcos were once political partners who won an overwhelming mandate to lead the nation's top two offices in 2022. The alliance crumbled this year over policy differences, including foreign policy and former President Rodrigo Duterte's deadly war on drugs.

Marcos' congressional allies are separately investigating the elder Duterte's war against drugs that led to more than 6,000 killed in anti-drug operations and alleged corruption over the younger Duterte's use of public funds during her tenure as education secretary.

Both have denied wrongdoing.

Duterte quit her Cabinet post in June.