More than 30 detainees escaped on Thursday after a bomb attacked a prison in the troubled southern Yemeni province of al-Dhalee, security officials in al-Dhalee told Xinhua.

The attack took place early morning when pro-independence protesters took to street and headed to the Security Administration building in the capital city of al-Dhalee, demanding the release of their fellow jailed people, said the sources.

"They approached the security building in an attempt to break in and threw a bomb at the nearby door of the building's prison," said the security official on condition of anonymity.

"The explosion almost smashed the prison's door," said the source, adding that "undetermined (number of) inmates and policemen were wounded and more than 30 prisoners escaped."

Additional security troops were deployed around and in the city of al-Dhalee in a bid to chase the escaped prisoners and arrest the rioters.

Meanwhile, in southern Yemeni province of Lahj, at least one southern protester was killed and two others injured Thursday when a demonstration to demand the release of pro-separatist prisoners sparked into clashes with security forces, according to the same source.

The Southern Movement demanding the southern part of Yemen to be seceded from the north organizes demonstrations every Thursday to press the government to release its supporters from prisons.

Northern and southern Yemen were unified in 1990 according to a deal between the People's General Congress and the Yemeni Socialist Party. However, the deal fell apart, leading to a crisis between the two allies, which developed into a civil war in 1994.

Nowadays, voices rise in South Yemen where secessionist sentiments are simmering, calling for disengagement from the north and the restoration of the southern state.

On Feb. 27, Yemen declared the state of emergency in al-Dhalee as a precautionary measure to thwart possible violence and riots by outlaws and destructive elements of the Southern Movement, state media reported.?