In scenes reminiscent of Iraq, a wave of blasts targeting government forces devastated the center of Aleppo, Syria's most populous city Wednesday. And a hardline jihadist group, Jabhat al Nusra - quickly claimed responsibility for the attacks - posting photographs and martyrs' messages online.
Syrian state media reported three suicide bombers detonated explosives packed into cars - killing dozens within a kilometer of the city's ancient citadel.
Analysts who follow the group tell CNN that Al Nusra has been preparing to intensify its campaign of suicide bombings for weeks. They believe the group has close links with al Qaeda's affiliate in Iraq. And this complex attack suggests it is becoming more accomplished at the sort of attacks that the Iraqi group has launched with such devastating effect.
The group said the operation was carried out over a period of five hours. The first attack was by suicide attackers with car bombs, followed by a gun attack by men disguised in Syrian military uniform, and then the detonation of two parked car bombs.
Noman Benotman, a former Libyan Jihadist now with the Quilliam Foundation in London, told CNN that according to sources with recent first-hand knowledge of Al Nusra's operations, the group had been gearing up for a major suicide bombing campaign in Syria.
"Their focus now is on recruiting suicide bombers. They want to copycat the Zarqawi model," Benotman told CNN, referring to the devastating campaign launched by al Qaeda in Mesopotamia leader Abu Musab al Zarqawi after U.S. troops occupied Iraq.
Benotman told CNN Al Nusra has been obtaining trucks and other vehicles, and stockpiling explosives, and is trying to match al Qaeda in Mesopotamia's ability to launch multiple attacks in different locations the same day.
But he says there is one major difference: unlike al Qaeda in Mesopotamia which has frequently targeted Shia civilians, Al Nusra's focus is on a broad array of Syrian regime targets.
Since last December there have been more than a dozen suicide bombings in Syria. More than half a dozen such attacks, including a complex and coordinated attack involving suicide bombers and gunmen at a military headquarters facility in central Damascus last week, have been claimed by Al Nusra.
Although explosives are harder to come by in Syria than in Iraq, where Sunni insurgent groups were able to use munitions looted from the former regime's stockpiles, Al Nusra has been able to buy explosives from overseas and convert munitions from heavy artillery and Katyusha rockets, according to Benotman.
The group's capabilities have also likely been strengthened by the arrival of volunteers from other Arab countries, he says - estimating that more than a thousand foreign fighters had likely joined a variety of rebel groups in Syria.
Although there are now fewer suicide bombings in Iraq than at the height of the insurgency, al Qaeda's affiliate there has shown it is still able to launch co-ordinated attacks. The group is believed to have been behind a wave of attacks on September 9 which were the deadliest since the withdrawal of U.S. troops.
According to Benotman, al Nusra has a strict vetting process for recruits, who must provide references before joining. He told CNN that al Nusra already probably has several hundred fighters, but is looking to recruit more - including men from other rebel groups.
Last month a video emerged of several dozen Free Syria Army fighters in Damascus announcing that they had joined the Jihadist group, according to Benotman. He said they stressed that one of the reasons they were joining was that they were impressed with Al Nusrah's fighting prowess.
"When it comes to al Qaeda you need to look at the impact, not the number of fighters. The capability to carry out operations is key and here it may not be easy to compete with al Qaeda," Benotman told CNN.
Given chronic weapons shortages among nearly all Syrian rebel groups, Al Nusra's suicide bombings may come to be seen as the most effective way to confront the regime, boosting its ability to recruit new fighters.
According to security analysts, increasing sectarian tension and regime brutality in Syria is also likely to play into Al Nusra's hands. "The longer the conflict goes on the stronger they will get," Benotman told CNN. He believes they have been behind most bombings in the capital.
Aaron Zelin, a research fellow at the Washington Institute of Near East Policy, who closely tracks the group, says that that in recent weeks Al Nusra had increasingly announced martydom operations, but also regularly claims responsibility for IED attacks, shootings and armed raids. According to Benotman the group has also carried out a series of attempted assassinations against Syrian officials using "sticky bombs" affixed to vehicles.
Though al Nusra has not pledged loyalty to al Qaeda, its propaganda suggests a close affiliation. It is hostile to the West and non-Sunni groups. Another sign, according to Zelin, is that al Nusra propagandists have received privileged access to password protected web forums used by al Qaeda and its affiliates. But the group may be wary of declaring allegiance to al Qaeda for fear of a backlash.
Benotman told CNN most of Al Nusra's fighters were Syrian, and included Syrian veterans of the Iraq insurgency and some who had recently returned from tribal areas of Pakistan. He said there were also several Arab al Qaeda fighters in the group. But little is known about Jabhat al Nusrah's leader Abu Muhammad al-Julani.
Al Nusra was almost wiped out by Syrian security forces earlier this year, according to Benotman. Citing sources with recent first-hand experience of its operations, he says a key operative in Al Nusra was arrested after a suicide bombing operation in Damascus and under severe torture gave up the names of dozens of members of the group in the capital, who were subsequently rounded up by Syrian security forces.
"The arrests almost broke the skeleton of the group because it came at that crucial time when it was trying to build up its operations, but it managed to reconstitute itself," Benotman told CNN.
According to Zelin, Al Nusra only released a half dozen statements and videos between the announcement of its founding in January 2012 and the end of April, but subsequently began releasing an increasing number of statements. According to a report last month by the Institute for the Study of War, Al Nusra claimed responsibility for more than sixty attacks in June compared to just seven in March.
Zelin told CNN that Al Nusra is now claiming responsibility for attacks more quickly, suggesting it is exerting greater control over operations and coordinating the operations of its military and media arms. He says the group's claim of responsibility for Wednesday's attack in Aleppo took less than 12 hours -- the fastest turn-around time ever.
Analysts believe Al Nusra will likely continue to strengthen its capabilities in the coming months, and not just in the country's two main cities. The growth of hardline Salafism in areas such as Deir Ezzor and Idlib in the last decade has provided Al Nusra with a potential pool of recruits, according to Mohanad Hage Ali, a Beirut-based international security expert. Hage Ali told CNN there are also a significant number of Syrian veterans of the Iraqi insurgency present in these two areas, including some skilled in urban warfare.