The official says today's jailbreak in Taiz came after the city's main prison was caught in crossfire between southerners fighting for autonomy or outright independence and the rebels, known as Houthis, who are backed by army units loyal to a former president.
He spoke on condition of anonymity because he was not authorized to speak to the press.
It was the third major jailbreak in Yemen since a Saudi-led air campaign against the rebels began on March 26.