Beirut, Lebanon - Last month, the leader of Syrian rebel group Jabhat al-Nusra - which has been steadily winning battles and gaining popular support since its inception in January 2012 - was forced to publicly clarify his group's relationship with al-Qaeda.

In a YouTube video posted on April 10, Abu Mohammed al-Jawlani stated: "The sons of Al-Nusra Front pledge allegiance to Sheikh Ayman al-Zawahiri," the former right-hand man of Osama bin Laden and the acting head of al-Qaeda.

With this declaration, Jawlani ratcheted up suspicions in the West that significant elements of the Syrian opposition are ideologically and tactically aligned with al-Qaeda. Nusra is now officially considered a "terrorist" organisation by the US State Department.

With fierce fighters, including veterans of battles in Libya, Iraq and Afghanistan apparently among its ranks, Jabhat al-Nusra is considered one of the most effective groups battling the regime of Syrian President Bashar al-Assad.

According to a report by the Quilliam Foundation, the group's roots can be traced back to the activities of deceased al-Qaeda leader Abu Musab al-Zarqawi during the early 2000s. During a journey from Afghanistan to Iraq to fight US forces, Zarqawi is said to have amassed fighters, sending some to Syria and Lebanon to establish branches of his network; so-called "guesthouses" to train and funnel fighters to Iraq.

Syria armed group claims allegiance to al-Qaeda

When it became clear the Syrian uprising of 2011 would devolve into war, many of these experienced fighters in Iraq came to Syria, the report says, with the goal of overthrowing Assad and establishing an Islamic caliphate in the Levant.

The experience of many Jabhat al-Nusra fighters distinguishes them from the often rag-tag Free Syrian Army cadres they sometimes fight alongside. The Quilliam report concluded that al-Nusra's leaders "can use their experience as jihadists in other countries to plan, identify goals, and strategise effectively, making them one of the most efficient groups fighting in the revolution".

Their main tactics are reflective of their training in asymmetric warfare in Iraq - car bombs, suicide missions, and the targeting of security forces. They also engage in more regular military activities, such as the capture of Army Base 111 following a successful siege.

Al-Qaeda fears

Jabhat al-Nusra has been regarded as a bogeyman in the West, and this preoccupation is readily apparent in statements from American policy-makers.

Just one month after Jabhat al-Nusra announced its formation, then-head US diplomat Hillary Clinton cited it and similar groups in Syria as one reason to withhold aid from the Syrian opposition. In a February 2012 interview with CBS, she said, "We know al-Qaeda's Zawahiri is supporting the opposition in Syria. Are we supporting al-Qaeda in Syria?"

But Syrians, watching a well-disciplined and organised group of fighters gain more and more ground against the Assad regime, are increasingly throwing their support behind Jabhat al-Nusra - in spite of its Islamist ideology, several Syrian activists and commentators say.

Support - or at least resigned acceptance - comes from many sides, some unexpected. Noor, a cosmopolitan young Syrian activist based in Turkey, said she's "not threatened by [al-Nusra] or their approach," as long as they continue to win battles against the regime.

Similarly, Ahmed Quseir, spokesman of the Homs branch of the General Authority of the Syrian Revolution, a network of opposition activists in Syria, says the Salafist leanings of al-Nusra "do not pose any risk" to the "freedom of Syrians", or the "type of power" that will emerge in Syria after the war.

In contrast, Abdelbaset Sieda, president of the Syrian National Council, emphasises that al-Nusra's radical ideology - a word he enunciates like an expletive - is "unacceptable" to Syria's "moderate social environment", which thrives on diversity, rather than narrow and literal interpretations of Islamic scripture.

'I do not have another choice'

Moderate Syrians' acceptance of Jabhat al-Nusra can be attributed to two main factors. First, they have all but given up hope of meaningful help coming from the West. Abdullah Alshamy, a member of the opposition affiliated with the Douma Revolution group as well as the Islamist Al-Faruq Brigades, said via Skype that given the increasingly dire situation Syrians find themselves in, "no one says no to help of any kind, whether it comes from al-Nusra or from America".

"Al-Nusra is just a group of people helping us against the Assad regime … I do not have another choice" but to support them, Alshamy said.

Al-Nusra is just a group of people helping us against the Assad regime … I do not have another choice. - Abdullah Alshamy, opposition member

Ma'moun Halal, an opposition member working with the Shahba Press Agency based in Aleppo, went further. "Jabhat al-Nusra fought Assad's regime at a time when the US and the West were saluting Bashar despite the massacres."

Between the massacres, the scorched earth, and the food and petrol shortages, Syrians seem ready to throw their support behind any group that can protect them and provide basic provisions.

Sieda, the Syrian National Council head, echoes these sentiments. In a phone conversation, Sieda emphasised the "brutality of the regime, which is using all kinds of weapons, and the indifference of the international community" as leading to "despair" that has driven average Syrians into the weapons-laden and wealthy arms of al-Nusra.

He predicted that with "collaboration" - the exact nature of which he could not specify - "many fighters would leave Jabhat al-Nusra and join the united army troops".

But it seems that Syrians are attracted to al-Nusra as more than a last resort. Activist sources cite al-Nusra's army-like discipline and an ethical code that seeks to protect the people, rather than exploit them, as has been the case with some other Free Syrian Army brigades. Halal speaks of the "vandalism and robbery" perpetrated by FSA fighters, not to mention the more sinister spoils of war that observers have heard whispers of.

Journalist Eli Kamisher relayed an anecdote told to him by a man in Kfranabel. "When Jabhat al-Nusra enter a village, all the thieves and rapists run away."

But Jawlani's declaration of allegiance to Zawahiri strikes even opposition figures sympathetic to al-Nusra as strange. "The relationship [between the two] is not accepted here, and they know that," Alshamy says.

But apart from grumblings, analyst Aaron Zelin believes that Jawlani's declaration will have little impact on the situation in Syria in the short term.

He contends that only introductions of Salafist ideology into the lives of moderate Syrians - such as "harsh punishments and narrow interpretations of sharia" - carry the potential to upset the cautious acceptance mainstream Syria has conferred onto al-Nusra.

That is already happening in some areas of Syria. In places such as Mayadin, Raqqa, and Aleppo, people have been lashed or jailed for drinking alcohol, not attending prayers, or mixing with the opposite sex, Zelin says.

When asked what will happen to Jabhat al-Nusra members after the war is over, should the opposition win, Alshamy expresses optimism. "I think some of them will work in Syria under the law of the country, and others will go back to their countries."

He admits, however, that thinking carefully about the post-Assad future is not high on many people's agendas. "All that is not important now. Now we should focus on staying alive."

Follow Stephanie d'Arc Taylor on Twitter: @sdarct