While the Obama administration and Congress continue to struggle over sending weapons to Syrian rebels fighting President Bashar Assad, the civil war is taking a brutal twist, with rebel groups now pitted against each other in an intense fight. Over the past few days alone, there has reportedly been a major assassination, a beheading and threats to fight “to the death.”

On Thursday, a senior Free Syria Army commander was shot dead by jihadi extremists from the al-Qaeda-associated Islamic State of Iraq and the Levant. The Free Syria Army (FSA) is calling the killing of Kamal al-Hamami, whose nom de guerre was Abu Basir al-Ladkani, a “declaration of war.”

Reports are conflicting as to exactly what happened, but according to Al Arabiya, Hamami – a member of the FSA’s Supreme Military Council – was meeting with members of the radical Islamic State of Iraq and the Levant in Latakia when they killed him.

Another report says he was ambushed and killed by members of the al-Nusra Front as he was on his way to a meeting they had scheduled with him.

Declaration of War: Syrian Rebels in a Bloody Fight with...Each Other

The Associated Press says this photo shows Syrian rebels running during heavy clashes with Syrian soldiers in the Salah al-Din neighborhood of Aleppo. The photo was taken by a citizen journalist on July 9, 2013 and was given to the Aleppo Media Center (Photo: AP)

One FSA commander was quoted in Israel Hayom as saying, “Our respond [sic] to the murder of Abu Basir [a.k.a., Hamami] will be tough. We will wipe the floor with his killers.”

“Extremist mercenaries who have infiltrated Syria are even more dangerous than Assad, and we will fight them to the death,” he added.

Spokesman for the largely secular and more moderate FSA Louay Almokdad tells Al Arabiya that the radical jihadi rebel killed Hamami “in cold blood using his personal gun and in front of eye witnesses that include FSA leaders.”

Almokdad said of the al-Qaeda linked rebels, “They consider us infidels and they [instructed] Abu Baseer’s [Hamami’s] companion to tell us: ‘We will kill you all.’”

On Saturday, rebels fought each other after al-Qaeda linked fighters tried to seize weapons from a Free Syria Army depot near Ras al-Hosn, north of Idlib province, according to Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

The Observatory also reports that late last week, dozens of FSA fighters were killed battling militants from the Islamic State of Iraq and the Levant.

The Observatory told AFP that an FSA battalion chief was beheaded and his brother was also killed.

Al Jazeera over the weekend reported that FSA and Islamic State of Iraq and the Levant rebels were battling over control of a strategic checkpoint in Aleppo.

“Some members of the groups now fear that tensions will escalate, hampering rebel efforts to overthrow President Bashar al-Assad. Analysts say divisions between Syria’s rebel groups are partly to blame for giving Assad’s forces the chance to regain the upper hand in the conflict” reports Al Jazeera.

AFP reports:

In the early days of the Syrian uprising, when opponents of the regime were desperate for assistance from any quarter, jihadist fighters were welcomed.

But activists and other rebels complain jihadist groups are power-hungry and seek to impose austere religious practices on an observant but heterodox population.

They have also been angered by arbitrary detentions and killings by jihadists, including the execution of a 15-year-old boy accused of uttering a blasphemous phrase.

“They are welcome if they help us fight the regime,” Colonel Abdel Rahman Suweis of the FSA Supreme Military Council told Al Jazeera.

“But if they want to cause strife, impose a new understanding of religion and make Syria another Afghanistan, we will take the necessary measures,” he added.

The Washington Post describes the qualitative difference between the rebel groups: “Jihadist groups such as the Islamic State of Iraq and the Levant — an offshoot of the main Islamist opposition group in Syria, Jabhat al-Nusra — are fewer in number than more moderate forces, but they are considered some of the best-equipped and most effective fighters on the battlefield.”

While the Free Syria Army was started by those who defected from President Assad’s military, the al-Qaeda linked groups rely on imported jihadis from Afghanistan, Iraq, Chechnya and even western countries in their effort to depose Assad and set up a hardline Islamist state.

As the U.S. debates if and when to start sending weapons to the FSA, the group continues to be out-armed by both the Syrian Army – supported by Iran and Russia – and the radical groups including the al-Nusra Front which reportedly receive weapons from al-Qaeda and Qatar.