Al-Qaida's Yemen branch, considered by Washington to be the most dangerous offshoot of the group, said in a statement circulated online Tuesday that it plans to avenge the execution of any of its members by Saudi Arabia.

The statement comes after unofficial reports in Saudi media suggested the kingdom was preparing to execute more than 50 convicted terrorists, among them al-Qaida-linked fighters as well as possibly Shiite opposition activists.

The Saudi Interior Ministry has told The Associated Press it has no information to provide regarding the reports and has declined to comment further.

Al-Qaida's Yemen offshoot, known as Al-Qaida in the Arabian Peninsula, said it heard about plans for the execution of its fighters in Saudi prisons.

"Their pure blood will not dry before we shed the blood of the soldiers of Al Saud," the group said in a statement in reference to the Saudi royal family.

"With God as our witness, we will not let you down — you, our prisoners — until you are released," the statement concluded.

The Associated Press could not independently verify the claim.

Al-Qaida fighters carried out deadly attacks targeting security forces, officials and Westerners in Saudi Arabia between 2003 and 2006. After a crackdown by Saudi security forces, many of the group's members fled to Yemen where they established AQAP.

The group has taken advantage of the civil war in Yemen, capturing much of the sprawling southeastern province of Hadramawt and its capital, Mukalla, earlier this year. In recent months it has wielded significant influence in parts of the strategic southern port city of Aden.

Saudi Arabia, meanwhile, has been bombing Shiite rebels in Yemen since March in an effort to restore the internationally recognized government to the capital, Sanaa.