The president of the Philippines will deliver a special address to the nation amid his allegations of a conspiracy by the opposition to oust him, the presidential spokesperson said Monday.

President Rodrigo Duterte's speech is scheduled to be held at 3pm on Tuesday, but no specific topic has been set, spokesperson Harry Roque said at a press conference.

On his arrival in the Philippines on Saturday after an official visit to Israel and Jordan, Duterte accused Senator Antonio Trillanes, the Communist Party and the Liberal Party - which jailed senator Leila de Lima belongs to and Vice-President Leni Robredo chairs - of plotting to overthrow him during the coming October, without providing evidence for the claim.

Trillanes has been holed up in the Senate for the past six days to avoid arrest after Duterte revoked the amnesty granted to him in 2011 for his involvement in three failed military coups over a decade ago.

All those accused by the leader have denied the allegations and say it is a strategy to draw attention away from the economic problems afflicting the country, which in August recorded a nine-year inflation rate high of 6.4 percent.

Robredo, one of Duterte's main political rivals, said on Sunday that the Liberal Party had become the government's scapegoat and all its shortcomings were attributed to the party, calling it unfair.

The Philippine president usually addresses the nation once a year in the State of the Union address, which is held on the third Monday of July.