Some sources say Samir Kantar was setting up a resistance movement in Golan Heights against Israeli occupation.

Beirut, Lebanon – Amid an array of Lebanese, Palestinian and Hezbollah flags, thousands gathered in Beirut’s southern suburbs on Monday to attend the funeral of Samir Kantar, 54, a high-profile member of the Lebanese Shia group Hezbollah, who was killed in a suspected Israeli air strike in neighbouring Syria.

The crowd marched behind the coffin – shrouded in Hezbollah’s yellow flag – as residents and mourners alike threw flower petals from the neighbouring balconies.

“His death will not stop the resistance against the enemy,” said Abdallah, one mourner attending the funeral.

Hours later, Hassan Nasrallah, Hezbollah secretary-general, vowed to avenge Kantar’s assassination, making it clear that the party [Hezbollah] has the right to respond to any act of Israeli aggression at a time and place of its choosing.

“The blood of Kantar is the same as the blood of any martyr in the resistance against Israel,” he said in an unusually sombre televised address.

“[Kantar] is one of us, a leader in our resistance, and he was killed by the Israelis in all certainty.

“It is our right to respond to his assassination at the time, place and means we deem appropriate. We in Hezbollah will practise this right, God willing.”

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Kantar, who spent some 30 years in an Israeli prison and was released in 2008 as part of a prisoner swap with Hezbollah, was killed on Saturday night after suspected Israeli air strikes targeted the building he was staying in, on the outskirts of the Syrian capital Damascus.

Also killed in the strike was Farhan Shaalan, a Syrian Druze from the occupied Golan Heights village of Ain Qinya.

While many commentators have described the two men as members of Syria’s pro-government National Defence Forces militia, such targeted strikes, according to one analyst, indicate more high-profile roles for the men than merely shoring up the Syrian government’s military positions on the ground.

Kantar was working on the development of a Syrian resistance movement that would focus on the liberation of the Golan Heights from Israeli occupation in southern Syria, the analyst says.

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Al Jazeera also spoke to a number of Syrian and Lebanese sources who knew both Kantar and Shaalan and were familiar with their work in Syria.

They say Kantar and Shaalan were both commanders within the Syrian National Resistance movement [SNR] – a little known group backed by the Syrian government, and advised and equipped by Iran’s Revolutionary Guard and Hezbollah.

Essentially made up of local Syrians from the areas close to Syria’s southern border with Israel, the SNR’s aim is to work on expanding and participating in the wider front of Hezbollah and its allies against Israel.

The creation and development of the group came about following a decision taken by the Syrian President, Bashar al-Assad, in 2013.

According to one Syrian official source, “until the start of the Syrian crisis, there had always been a military balance in the south between the Syrian army and the Israelis.

“When the Syrian army positions [on the borders] came under attack by Syrian opposition armed groups in that area, under the cover of the Israelis, the president took the decision to allow Hezbollah to help with the development of a home-grown resistance movement against Israel from the Golan Heights”.

The source said “the Israelis changed the rules of the game by getting involved with the [Syrian] opposition groups in the south”.

The southern borders were specifically viewed as critical by the Assad government since Syria is still at war with Israel.

The sources say Kantar’s newly formed group began working on two fronts: assisting the Syrian army in its fight against rebel groups in the area, and setting up a local resistance group.

Kantar, according to both Lebanese and Syrian sources, is said to have been instrumental in recruiting and training locals – the majority of whom are Druze from the Golan Heights area and its surroundings – focusing his efforts on carrying out operations along the border.

Shaalan was a former commander of the pro-government National Defence Forces in Jaramana, until he was brought into the SNR in 2014 to work alongside Kantar on beefing up the movement’s capabilities.

“The Israelis targeted [Kantar and Shaalan] because they want to weaken and finish the nascent resistance movement in the Golan Heights,” said a Syrian security official, adding that Israel was keen on maintaining a sphere of influence in southern Syria and the development of the SNR is problematic for them.

READ MORE: Syria’s Druze reject calls for anti-government uprising

Information on the SNR and its activities remain sparse; little is known about the numbers of cadres involved, who they are and the type of military equipment they have access to.

While Hezbollah refuses to formally admit any connection with the group, one Lebanese official source said Iran was providing assistance to the group.

“Iran helps with training, weapons, and funding [of the SPR],” said the Lebanese source.

“The idea is not to put entire Hezbollah battalions there, but rather to work with people from the area instead, to set up a home-grown resistance movement. Therefore the SNR is not necessarily Shia; it’s made up of Druze and Sunnis from there.”

According to Hossam Matar, a political analyst who is close to Hezbollah circles, the emergence of this group is hardly surprising.

“Nasrallah has since declared that both the occupied Golan Heights [in Syria] and occupied Shebaa Farms [in Lebanon] represent one front,” he told Al Jazeera.

“Hezbollah, as well as its allies, has said it is ready to help train local resistance groups in the battle against Israel, and this particular group is focused on Israel. It is not working on the internal conflict [inside Syria].”

The SNR, says Matar, is still limited in its capabilities.

“It is currently in its early phase. It still needs more time before it can take any serious action. The latest operation shows it is still weak.”

Nonetheless, the presence of the SNR in the occupied Golan Heights enables Syria to reset the balance of power in the area.

“The main goal is to deter Israel from intervening more in the Syrian crisis, both directly and indirectly,” said Matar.

“In the future, the Golan Heights is the most appropriate place to act against Israel. And because of all the chaos in the country, the margin for political action is much wider in Syria than in Lebanon.”