More than 100 people were killed and wounded when rebel suicide bombers struck overnight at an Air Force Intelligence compound near the Syrian capital of Damascus, Reuters reported.
The BBC reported that dozens died in the attack, according to activists. Official figures of the death toll have not been released.
Both news outlets reported that the militant Islamist group al-Nusra Front claimed responsibility for the attack. According to the BBC, "AFI is seen by some as the elite agency of Syria's intelligence empire," a belief that seemed borne out by the attackers, according to a statement.
"The decision was taken to hit Air Force Intelligence because it is one of the most notorious security divisions, and a citadel of repression whose extent is known only to God," said an Al-Nusra statement posted to social media, according to Reuters.
The insurgents said they mounted the attack because the compound was used as a center for torture and repression in the crackdown on the 18-month-old revolt against President Bashar al-Assad.
USA Today said Syrian rebels trying to topple President Bashar Assad are increasingly targeting security compounds and symbols of the regime in Damascus.
In July, an attack on the National Security headquarters killed the defense minister and two other senior security officials.
More from GlobalPost: Full coverage: Damascus bombing
The latest bombing, which occurred on the border near Damascus, was believed to have left at least 100 security personnel killed or wounded, but no official figures have been released.
"Big shockwaves shattered windows and destroyed shop facades. It felt as if a bomb exploded inside every house in the area," said one resident of the suburb of Harasta, where the compound was located.
Residents and opposition activists told Reuters the explosion which could be heard across the city was followed by a fierce gun battle. Video footage taken by activists, which could not be independently verified, showed a large explosion.