Caracas: The head of Venezuela's opposition-led legislature proclaimed himself "acting president" in a bid to oust leftist leader Nicolas Maduro, winning immediate backing from regional powers led by the United States.

The move by Juan Guaido capped days of political drama that has seen seven protesters killed since Tuesday night. "I swear to formally assume the national executive powers as acting president of Venezuela to end the usurpation, (install) a transitional government and hold free elections," Guaido told supporters.