Sana'a: Unidentified assailants on Monday set an explosion to an important gas pipeline in the Yemen's northern province of Shawba, hours after suspected Al Qaida  militants raided the intelligence headquarters in Aden, local sources said.

Witnesses from Shabwa said that a huge explosion occurred in Jardan district damaged a gas pipeline that carries gas from the province of Mareb to the export terminal in Balhaf, Shabwa. 

In a short statement posted on its website, Yemen LNG said "Yemen LNG confirms the sabotage of the 38 inch gas pipeline that links the block 18 to the Balhaf terminal on the Gulf of Aden. The explosion occurred at 01h15 on 21 August 2012 at 171 KM North of Balhaf Liquefaction Plant."

No one has claimed responsibility for the attack that struck near the country's most expensive industrial investment.

Also in the south, local residents in the port city of Aden said on Monday night that security guards of the intelligence headquarters in the city exchanged fire with car-borne attackers.

After firing at the police, the attackers tossed a bomb at the building before fleeing. No one was reportedly hurt in the attack.

On August 18, the same building came under deadly attack by suspected Al Qaida militants, killing at least 14 soldiers and partly damaging the building.