As aid agencies prepare to deliver food to Madaya, on the outskirts of Damascus and two other besieged towns in Idlib province, an estimated 400,000 people are living under siege in 15 areas across Syria, according to the UN.

A deal struck on Saturday permits the delivery of food to Madaya, currently surrounded by forces loyal to Syrian President Bashar al-Assad, and the villages of Foua and Kefraya in Idlib, both of which are hemmed in by opposition fighters.

Due to a siege imposed by the Syrian regime and the Lebanese Hezbollah group, an estimated 42,000 people in Madaya have little to no access to food, resulting in many deaths by starvation so far, according to the charity Doctors Without Borders (MSF).

Reports of widespread malnutrition have emerged, some of them suggesting that Madaya residents are resorting to eating grass and insects for survival.

On December 26, Syrian regime forces set up a checkpoint and sealed off the final road to Moadamiyah, an opposition-controlled town on the outskirts of Damascus, demanding that opposition groups lay down their arms and surrender.

The Moadamiyah Media Office, run by pro-opposition activists, estimates that 45,000 civilians have been stuck in the area for more than two weeks.

The organization said on Saturday that a siege that started in April 2013 and lasted a year, resulted in the deaths of 16 local residents due to a lack of food and medicine.

It said the current conditions had killed one local resident so far this year: an eight-month-old boy who died from malnutrition on January 10.

Dani Qabbani, a Moadamiyah-based media activist, said the child died because of "the crippling siege being imposed by Assad's militias".

"They couldn't help him here in the only field hospital in the city," he told Al Jazeera. "Assad's checkpoints prevented his family from hospitalising him in Damascus.

"If the situation continues for another week, we are expecting a disaster for the 45,000 civilians [in Moadamiyah]."

Describing the local population as worn down and scared, Qabbani said "they don't want to go through what they did in 2013 again".

Sharif Nashashibi, a London-based analyst of Arab political affairs, says the government-imposed sieges in places like Moadamiyah and Madaya have put opposition fighters under "double pressure".

"These sieges don't just wear down the fighters, it also causes them to see the population around them suffering and raises the concern that the population could turn against them," he told Al Jazeera.

"These sieges are war crimes. The regime is collectively punishing the population of that area because of the presence of 'enemy' fighters."

The UN reported in December that the Syrian regime and allied militias have also placed under siege more than 181,000 people in the Damascus outskirts, including Daraya and Ghouta, as well as in Zabadani, near the Lebanon border.

PHOTO CAPTION

Children hold a poster during a sit-in calling for the lifting of the siege off Madaya, in front of the International Committee of the Red Cross (ICRC) in Beirut, Lebanon January 8, 2016.

Al-Jazeera