The head of Venezuela's opposition-controlled parliament challenged President Nicolas Maduro on Friday, saying he is ready to assume country's presidency himself until free and fair elections can be held.

Juan Gerardo Guaido Marquez made the announcement at an anti-government rally in the capital, Caracas on Friday, a day after Maduro was sworn in for a second term, deemed by many as "illegitimate". 

Guaido, who leads the internationally-recognised National Assembly, said there was no doubt that Maduro was a "usurper" and called for the support of the public, armed forces and international community in restoring constitutional order to Venezuela. 

"I assume the duty imposed by the Constitution and Article 333, which obliges all Venezuelans, vested with authority or not, to fight for the restitution of constitutional order," the National Assembly quoted Guaido as saying in a series of posts on Twitter.

"The Constitution gives me the legitimacy to exercise the charge of the presidency of the Republic to call elections, but I need the support of the citizens to make it happen," he said before calling for massive protests on January 23.

The date is significant for Venezuelans as it marks the anniversary of the end of the Marcos Perez Jimenez dictatorship, which ruled the country from 1948-1959. 

The call from the opposition comes a day after Maduro began his new six-year term following a controversial win in a 2018 election that was largely boycotted by the opposition.

Maduro dismissed the National Assembly as a "show of little boys", telling reporters that while the "crazy and immature minds at the head of the opposition" were holding their demonstration, he was working. 

Iris Valera, Venezuela's minister for penitentiary affairs, said she already has a cell ready for Guaido.

"I hope you quickly name your cabinet to know who will accompany you," she said on Twitter on Thursday.