Updated

The leader of the Yemen-based al-Qaida offshoot has vowed to free fellow militants from prisons everywhere and urged them to remain faithful to the terror group's ideology.

The message by Nasser al-Wahishi, posted on militant websites Monday, warns al-Qaida prisoners not "to be lured by their jailers" and promises that "victory is imminent" to ensure their freedom.

The note by al-Wahishi, a onetime aide to Osama bin Laden, comes after last week's closure of 19 U.S. diplomatic missions triggered by the interception of a secret message between al-Qaida chief Ayman al-Zawahri and the Yemeni branch's leader about plans for a major attack.

It also follows an announcement by Yemeni authorities that they had discovered an al-Qaida plot to target foreign embassies in Sanaa and international shipping in the Red Sea.