A coalition of armed anti-government groups, the Army of Conquest, has captured all of a strategically important military base in the northern city of Aleppo, Syrian rebels said.  

The opposition forces, who already control the countryside and areas southwest and east of Aleppo, said on Saturday that they now control the base in the Ramosa quarter in southwestern Aleppo.

The Syrian Observatory for Human Rights (SOHR), a UK-based monitoring group, also said on Saturday that the same armed rebel coalition "took control of the armament school, where there is a large amount of ammunition, and a large part of the artillery school".

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However, Syrian state television disputed the claim, saying that government forces pushed the rebel fighters back, killing hundreds of them in the process.

Saturday's conflicting claims came a day after the  Army of Conquest said they had stormed the major army artillery base, and were fighting to take the other military academies adjoining it.

The artillery base is almost 2km from the besieged opposition area.

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It has a huge supply of ammunition and is used regularly to shell parts of the city held by opposition forces.

"There are two suicide bombers who have driven into regime posts inside the artillery base," Abu al-Walid, a fighter with Ahrar al-Sham, told Reuters news agency on Friday, adding that there was fighting inside the base.

Hundreds of fighters clashed with government troops only a few hundred metres from each other in parts of the artillery base after breaking into government defences around the heavily fortified compound, the rebels said.

For its part, the Syrian army said the attack on the artillery base and two major military academies had been foiled, with hundreds of fighters killed and much of their armoured vehicles and tanks destroyed.

It said the assault was the biggest by rebels against government-held areas in the past few years.

"Today there was a large-scale attack by the terrorist armed groups and they used all types of weapons, but we are fighting this attack and will defeat them," Brigadier-General Deeb Bazi, the head of one of the military academies targeted, told Reuters.

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Al Jazeera's Reza Sayah, reporting from Gaziantep, on the Turkish side of the Syria-Turkey border, said the fighting in Aleppo is described by many as "the decisive battle for Syria".

"The impression is that if the government manages to take over Aleppo, they will gain momentum and take away leverage from the rebels - there will no longer be an incentive to go on the negotiating table with the rebels," he said.

Rising death toll

Once Syria's economic powerhouse and the country's biggest city, Aleppo has been divided between government forces and rebels since the summer of 2012.

The government siege of opposition-held districts began on July 17 and has raised fears of a humanitarian crisis for some 300,000 people trapped in rebel-controlled areas.

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According to the SOHR, at least 115 civilians, including 35 children, have been killed in the city since the fighters began an assault on Sunday to break through a strip of government-controlled territory in order to reconnect their area of control in western Syria with the encircled sector of eastern Aleppo.

The deaths include 65 people, among them 22 children, killed in opposition fire on government neighbourhoods, according to the SOHR, which gathers information from a network of activists in Syria.

Another 42 people, including 11 children, have been killed in strikes on eastern Aleppo.

It reported five more deaths in rebel fire on the Kurdish-majority Sheikh Maqsoud district of the city.

Battle in Manbij

In a separate development, a coalition of Arab and Kurd fighters trying to oust fighters from the Islamic State of Iraq and the Levant (ISIL) from Manbij took "almost complete control" of the key town south of the Turkish border on Saturday, according to the SOHR.

Backed by air strikes by the US-led coalition, the Syrian Democratic Forces (SDF) had launched its offensive to retake Manbij on May 31. 

"The Syrian Democratic Forces took control of Manbij on Saturday and are combing the city in search of the last remaining jihadists," the SOHR said.

The Manbij Military Council - a key component of the SDF - said fighting was still ongoing in the town.

"The battles are continuing near the centre of the town. We are in control of 90 percent of Manbij," said spokesman Sherfan Darwish.

The town in Aleppo province had served as a key transit point along the supply route of ISIL, also known as ISIS, from the Turkish border to Raqqa, the de facto capital of its self-styled "caliphate".

The Syrian conflict began as a mostly unarmed uprising against President Bashar al-Assad in March 2011.

However, it quickly escalated into a full-blown civil war, with more than 280,000 people now estimated to have been killed in fighting between the government, the opposition and other armed groups.

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Source: Agencies