Around 1,200 prisoners broke out of a prison in Yemen on Tuesday using the clashes in the prison as an opportunity.
The incident is regarded as the biggest prison break in which Yemeni militants have escaped in recent years.
Al Qaeda suspects are also among those who have escaped.
"Groups of al Qaeda supporters ... today attacked the central prison in the city of Taiz and more than 1,200 of the dangerous prisoners escaped," a security official said according to state news agency Saba.
Some of the prison breakers were "suspected of belonging to al Qaeda" but they escaped during fierce clashes between militia forces in the city, another local official told Reuters.
Shi'ite Muslim Houthi fighters came to the city of Taiz in March, after advancing from their base in the capital Sanaa.
Houthis have been the target of air strikes conducted by a Saudi-led coalition since they forced the Yemeni President Abd Rabbuh Mansour Hadi out of the country in March.
Despite three months of heavy air strikes, the military intervention has still not been successful to repel Houthi militias and units in Yemen's army that are loyal to the country's ex-president, Houthi ally Ali Abdullah Saleh.
The army forces that are linked to Saleh, permitted the prisoners to escape while the militiamen who are called "popular committees" by their backers, closed in on the prison, the security official added.
"Heavy fighting took place near the central prison and the popular committees approached and seized control of the area, but Saleh's forces opened the prison doors.”
Another prison break took place in the eastern city of Mukalla, where a group of al Qaeda militants escaped from a prison in April.
Al Qaeda and some other groups criticise the Houthis, calling them renegades who are worthy of death.
Harsh clashes between Al Qaeda and Houthis still continue in different areas of central Yemen.