By Tom Coghlan, Hannah Lucinda Smith and Sara Elizabeth Williams

A succession of defeats in both the north and south of Syria has left the Assad regime looking weaker than at any point in the country’s four-year civil war and its forces increasingly demoralised.

A newly formed grand alliance of rebel groups named Jaish al-Fatah (The Army of Conquest) has seized a series of urban areas and military bases in the north of the country since December, inflicting a series of damaging blows to the government.

The forces, including hardline Islamists allied to al-Qaeda, took the city of Idlib last month. The strategic town of Jisr Ash-Shughur fell last week after limited government resistance and the so-called “Brick Factory” military base was seized on Monday. It was the last significant government-held base in Idlib province.

Meanwhile, sources inside the country’s second city, Aleppo, said there were rumours of a Syrian government withdrawal under fire from multiple rebel groups — which would be a hugely significant blow.

The rebel gains now also threaten the Mediterranean coastal city of Latakia, the spiritual home of the Alawite minority that dominates the Assad regime, for the first time since 2013. On Thursday Syrian government forces fought fierce battles in the Jabal al-Akrad mountains, close to the ancestral home of the Assad family. “The capture of the peaks would put the Alawite villages in our firing range,” said a rebel commander based in Idlib.

Islamist rebels have used suicide car bombs to hit government strong points and have used American TOW missiles against Syrian government tanks.

Inside government-held areas of Aleppo, there is growing disquiet, according to locals. “It seems inevitable that the regime will give the city up,” said one Syrian refugee in Turkey who remains in contact with his family in the government-held side of the city.

Opposition activists and citizen journalists within the city report that the regime has emptied Aleppo’s central bank and museums and that high-ranking officers are moving their families out of the city and towards Latakia and Tartus, near the coast. While none of the rumours can be confirmed, they point to a general shift in the mood in Aleppo, which had often appeared to be on the brink of falling to regime forces last year.

The new-found rebel strength is linked by analysts to a boost in military support for Islamist rebel groups — including the al-Qaeda-affiliated Jabhat al-Nusra — from Qatar, Turkey and Saudi Arabia, despite opposition from the United States.

“The Saudis, the Turks and the Qataris all agree now that Assad must go,” said Professor Joshua Landis, director of the Center for Middle East Studies at the University of Oklahoma. He described American strategy in the country as “Awol”.

A passing-out parade for one Islamist group in the Damascus suburbs this week — Jaish al-Islam — showed more than 1,500 marching fighters in identical military uniforms and helmets. It was equipment that analysts said could only have come with the backing of a state. Saudi Arabia is thought to fund the group, which is commanded by Zahran Alloush, the son of a Saudi religious scholar. He went to Istanbul last month to consult regional officials.

In the south of the country rebel forces have also made gains, capturing the military base of Busra and the last government-held crossing place into Jordan at Nassib.

Government areas are experiencing increasing privations, according to local people. Syrian government supplies of hard currency have shrunk from $20 billion to $1 billion since 2010. The regime has begun selling passports to Syrian refugees in neighbouring countries for an inflated price of $400 each, double the previous cost. The sum must be paid in dollars or euros.

Government forces have become increasingly reliant on external Shia Muslim volunteer forces from Iran, Iraq, Afghanistan and the Lebanese militia Hezbollah. Israeli officials say that the Syrian army is a depleted force in the south of the country and has drawn its remaining combat-capable divisions back to the approaches of Damascus.

Despite the setbacks to the regime, regional officials still regard its control of a rump state covering Damascus and the coastal strip as secure. “What we are seeing is not the end of the road but what we are seeing is the regime tired, the regime exhausted,” said one senior Gulf state official. “The collapse of the positions in Idlib and the south are still not strategically significant.”