A number of inmates, including several al-Qaeda fighters, have escaped from a prison in the southern Yemeni port city of Aden after tunnelling their way out in the second such spectacular jail break this year, officials have said.
A prison officer said at least 10 men escaped early on Monday through an up to 40m-long tunnel, which took the inmates from under the western side of the Aden jail to near a petrol station outside the prison walls.
A security official said 15 men fled in the prison break, including 12 convicted for the killing of security officials and a bank robbery.
The discrepancy in the number of escaped prisoners could not be immediately reconciled. Both officials spoke on condition of anonymity because they were not authorised to speak to the media.
Yemen, the Arab world's poorest nation, has been wrecked by months of political turmoil and unrest.
A popular uprising against longtime President Ali Abdullah Saleh's rule, inspired by other Arab Spring revolts that toppled autocratic rulers in Egypt and Tunisia, has been met by a fierce government crackdown.
The crackdown triggered widespread defections earlier this year by soldiers and officers who joined the protest movement.
Powerful tribes and their armed fighters also turned against Saleh and waged battles against his forces.
Yemen is also home to Al-Qaeda in the Arabian Peninsula (AQAP), which the US considers the network's most active and dangerous offshoot.
Fighters with links to the group have taken advantage of the country's turmoil to seize control of several towns in the south.
In 2003, 11 al-Qaeda fighters convicted for the 2000 bombing of the USS Cole, which killed 17 US sailors and injured 39 others, escaped from the Aden prison.
In 2006, 23 fighters from the same group broke out of a detention facility in Sanaa, including Nasser al-Wahishi, who went on to become AQAP's leader.
In June, nearly 60 suspected al-Qaeda fighters tunnelled their way out of a prison in the southern city of Mukalla.
Investigations into the breakouts and subsequent trials showed that some prison security officers were involved in helping the convicts flee and several officers have been jailed.