BEIRUT: Syrian rebels are launching a major operation to take control of the strategic eastern city of Deir al-Zor after pushing out government forces from oil-producing areas around it, a rebel commander said.

If they seize the city, the rebels will control a whole province for the first time in the 22-month-old Syrian uprising against President Bashar al-Assad.

Ibrahim Abu Baker, leader of the powerful Al-Qadisiyah Brigade, said his rebel force, along with Islamists from Jabhat al-Nusra and Arab fighters, had surrounded Deir al-Zor on four sides in the build-up to the operation.

"The countryside is liberated, what is left of the province (of Deir al-Zor) is the city itself," he told Reuters from the province via Skype. "All brigades are taking part in this... We are in charge of the eastern side of the city."

Deir al-Zor extends northwards along the Euphrates River from the border with western Iraq, home to Sunni Muslim tribes which support the Syrian rebels.

Another rebel from Abu Baker's brigade said on Monday that fighters had started the first stage of the operation by targeting tank fire against three military targets inside the city and besieging the final army stronghold on its outskirts.

"We are now surrounding (the army's) '113 Brigade' which is the last point in the countryside before we are totally focused on the city," said the rebel fighter who used the name Abu Mazen. "When we liberate the city some brigades will stay to take care of it and the rest will march to Damascus".

Abu Baker said for months the rebel forces had only limited access to the city, which contains powerful security branches and a military airport.

But two weeks ago, with help from Jabhat al Nusra, they captured a security branch located near a strategic bridge on the Euphrates, opening the eastern bank to the rebels.

"After liberating the bridge we started sending aid and weapons to the fighters inside the city.. And also sending reinforcements," he said. "Now there is nothing to stop us from entering the city."

The Qadisiyah Brigade is one of the most influential in the province and has fought fierce battles with government forces.

It already controls wheat silos, a textile factory and a gas distribution centre. It is composed of eight battalions with fighters from across the country, Abu Baker said.

"FIGHTING FOR GOD"

The revolt against Assad has taken on a sectarian hue, pitting the mainly Sunni rebels against an army whose senior ranks are dominated by Assad's minority Alawites.

Like most brigades fighting in Syria, Abu Baker said his force is composed of Syrian Sunni fighters only. "We are Islamists, we went out just to support our religion. This is why we took to the streets. We respect other religions but we are Sunnis and we want a Sunni to rule not an Alawite."

Other Arab fighters from Iraq and Saudi Arabia are also fighting in the province, he said. "They are a separate faction, but our relation with them is good. We welcome anybody who wants to join us in jihad against Assad whether Saudis or Iraqis."

"...Our goal is one and we are fighting for God."

Rebels control the Syrian side of the Albu Kamal crossing into Deir al-Zor province, a key supply route from Iraq, but the Iraqi government has sometimes closed the crossing fearing a spillover of sectarian conflict into their country.

Iraq's government faces its own Sunni protests, with a series of demonstrations in the Western province of Anbar.

With protests in Iraq increasing, Syrian rebels are keeping a close eye on their neighbour and some are anticipating clashes with the Shiite-led government in Baghdad.

"The Sunnis in Anbar are helping with weapons and ammunitions," Abu Baker said. "Their days (of fighting) will come soon and Inshallah (God willing) we will go to jihad with them. Those Sunnis are our brothers."