Philippine authorities handed a subpoena to Vice President Sara Duterte’s office Tuesday, inviting her to answer investigators' questions after she publicly threatened to have the president, his wife and the House of Representatives speaker assassinated if she were killed in an unspecified plot herself.

Philippine Vice President Sara Duterte on Tuesday denied she was plotting to kill President Ferdinand Marcos, saying her comments that sparked a government probe only reflected "consternation" with her one-time ally.

Philippine President Ferdinand Marcos on Monday vowed to fight back against what he called reckless and troubling threats against him, speaking out after his estranged vice president said he would be assassinated if she herself were killed.