Harrowing new details have emerged from the besieged Syrian city of Madaya revealing how starving citizens have been reduced to living off salt and water to survive.

The rebel-held former holiday resort has been under siege by soldiers loyal to president Bashar al-Assad for six months, leaving electricity and food in short supply as winter grips the city.

There are an estimated 40,000 people still trapped inside the city, which is surrounded by minefields. Many of the inhabitants have had to find basic nourishment from grass and leaves after eating all of Madaya’s stray cats and dogs.

Weakened, cold and starving to death in Syrian town

Now it has emerged that the most desperate inside Madaya are gripping on to life on a diet of nothing more than salt and water, leaving them malnourished and on the brink of death.

“A lot of people are surviving on water and salt only,” a humanitarian activist in Madaya told Al Jazeera under condition of anonymity. “They dissolve salt into the water just to kill the hunger pangs they are dying from. Malnourishment is killing people.”

A toddler is held up to the camera in this still image taken from video said to have been shot in Madaya, Syria (Reuters)

At least 23 people have already died of starvation in Madaya since December 1, according to Doctors Without Borders, with images of their emaciated corpses being widely shared on social media. Tiny babies are among the dead.

Videos are photographs from inside the city show badly malnourished men, women and children clinging to life, their frail bodies looking more like skeletons than living human beings.

A starving boy is seen in a picture released by the Local Revolutionary Council in Madaya (AP)

One image shared on Facebook appears to show a desperate citizen preparing to slit the throat of a cat while other photos show malnourished children eating a broth made of olive tree leaves and water.

“There are no more cats or dogs alive in the town. Even tree leaves that we have been eating have become scarce,” local resident Abu Abdul Rahman told Al Jazeera.

Hardly anybody has managed to escape the city in recent weeks, with at least four of those attempting to do so being blown up by landmines or taken out by sniper fire over the past month.

The town has become “an open-air prison,” Brice de le Vingne, director of operations for Doctors Without Borders, said in a statement.

Fighting over Madaya, which fell into rebel hands in 2012, was supposed to have ended last summer under a cease-fire deal that also encompassed two rebel-surrounded towns in northern Syria.

According to the terms of the cease-fire, rebel fighters from Madaya and nearby Zabadani were escorted by the United Nations to Turkey, and government loyalists from the towns of Foua and Kefraya were permitted to leave for government-held areas of Syria.

The deal stipulated that food aid and other supplies be allowed to reach civilians inside the towns. But only one delivery was made to Madaya, on 18 October, and residents since then have almost entirely run out of food.