CARACAS: Venezuelan President Nicolas Maduro on Monday said a move by the opposition-controlled National Assembly to extend its term into next year was "unconstitutional," and called on the South American country's justice system to "do its work."

The National Assembly, overseen by opposition leader Juan Guaido, has declared Dec. 6 parliamentary elections in which allies of Maduro's ruling socialists won a majority as "illegitimate", and over the weekend voted to prolong its mandate.

Venezuela's mainstream opposition parties boycotted the vote on the basis that they would not be free and fair. Maduro, who calls Guaido a US-backed puppet seeking to oust him in a coup, has said the electoral conditions were as transparent as when the opposition won a majority in the parliament in 2015.

"In the face of unconstitutional claims to self-proclaim term extensions that are not warranted, we trust that the justice system will do its job with an iron fist," Maduro said in a state television appearance with members of the military.

The parliament's move to extend its term comes as dozens of legislators facing criminal investigation for alleged crimes like treason have fled the country. Others have expressed unwillingness to continue serving in congress due to what they describe as persecution the government.

Guaido labels Maduro a corrupt dictator who has overseen the economic collapse of the once-prosperous OPEC nation.

Guaido is recognized by dozens of Western democracies that have questioned the legitimacy of Maduro's 2018 re-election vote as Venezuela's rightful leader, due to his position as the National Assembly's speaker.