The vice-president of Venezuelan National Assembly, Edgar Zambrano, was towed to prison after he refused to exit his vehicle to be arrested.
The arrest comes a day after Venezuela's Supreme Court ordered that Mr Zambrano and six other National Assembly deputies be charged with treason for their alleged participation in a failed military uprising.
US Embassy in Caracas called the detention "illegal and inexcusable" and warned that if he was not released immediately, there would be consequences. While the EU said the arrest was "another fragrant violation" of Venezuela's constitution and described it as "a politically motivated action aimed at silencing the National Assembly".
The arrest is one of many incidences of escalation within Venezuela as tension between Mr Guaidó and sitting president Mudrado, since Guiado declared himself Venezuela's acting leader in January.