CARACAS, Venezuela — Hundreds of thousands of Venezuelan opposition supporters poured into the streets on Saturday, heeding a call from their leaders to stage another day of peaceful protests against President Nicolás Maduro’s authoritarian rule in hopes of capitalizing on international pressure to force him from power.

In another boost for the opposition, a top air force official and a man identifying himself as a Venezuelan ambassador released separate videos breaking with Mr. Maduro and pledging allegiance to Juan Guaidó, the opposition leader. They were two of the highest-level defections yet in the country’s growing political crisis.

“Ninety percent of the armed forces do not support Nicolás Maduro,” said Division Gen. Francisco Esteban Yánez Rodríguez, the air force official. “I ask my comrades in arms to not turn their backs on the people of Venezuela, do not repress anymore.”

In another video released in the evening, a man identifying himself as Jonathan Velasco, the Venezuelan ambassador to Iraq, said Mr. Guaidó “stood on the right side of history” and was the country’s rightful leader.