MANILA – President Rodrigo Duterte will not allow "extensions in perpetuity" of martial law in Mindanao, Malacanang said Thursday, after opposition lawmakers again assailed the constitutionality of its extension before the Supreme Court.

• Opposition solons ask SC for TRO on martial law extension

Congress recently extended martial law for one year, until the end of 2018, as it acknowledged the threat from Islamic State militants who laid siege on Marawi City for 5 months until October this year.

• Congress extends Mindanao martial law until end of 2018

"Martial law in perpetuity is a scenario that neither the President, Congress or the Supreme Court will allow as it is patently unconstitutional," Presidential Spokesperson Harry Roque Jr. said in a statement.

Opposition lawmakers said the extension violated the Constitution but Roque said it had "legal and factual bases." The spokesman said the government was ready to defend its decision in court.

The opposition said there was no actual state of rebellion in Mindanao to justify the extension of martial law and that Duterte’s allies in Congress approved the request for extension "with inordinate haste."