Juan Guaido accused Nicolas Maduro of using his uncle,to threaten him as he returned from an international tour rallying support to topple the president.
After meeting with the Colombian President and US Secretary of State,Guaido plans to travel to the World Economic Forum in Davos,Switzerland.
The opposition leader and his supporters pushed through rows of National Guardsmen blocking Congress,holding a swearing-in ceremony after power was cut.
Luis Parra insisted rules were followed when he was elected head of the National Assembly when Maduro security forces blocked many in opposition from voting.
Fifteen countries including the US are trying to devise new measures to support a re-establishment of democracy and respect for human rights in Venezuela.
The tense 11-hour stand-off created a diplomatic embarrassment for Brazil's right-wing government as it hosts a BRICS summit.
Trump's latest executive order imposes a full embargo on Venezuela's government,putting it on a footing similar to Cuba,Iran,North Korea and Syria.
Maria Lourdes Afiuni,who was arrested nine years ago without a warrant,confirmed her release on Twitter.
The plan allegedly involved an attack on the headquarters of the country's intelligence agency to release a detained general and install him as president.
US President Donald Trump said on Monday that Russia told the United States it had removed most of its people from Venezuela.
Canada has played a key role within the Lima Group along with nearly a dozen Latin American nations to try to rein in Nicolas Maduro.