A member of the Syrian pro-government forces stands at the entrance of the besieged rebel-held Syrian town of Madaya as residents wait for a convoy of aid on January 14, 2016. (Louai Beshara/AFP/Getty Images)

Hundreds of thousands of people across Syria in areas besieged by government forces and opposition fighters are at risk of starvation and worsening malnutrition, U.N. officials, aid workers and activists warn.

The warring parties are cutting off food and medicine to more than a dozen areas, causing civilians to die and complicating renewed peace efforts to end the country’s civil war. Disturbing images on social media purporting to show emaciated men, women and children in the town of Madaya, which has been blockaded by government forces, have in recent weeks added urgency to the issue.

“As the conflict goes on and on, the situation on the ground is collapsing, especially in areas that are under siege,” said Pawel Krzysiek, a spokesman for the International Committee of the Red Cross who is based in the Syrian capital, Damascus.

Even before Madaya, sieges were common in the Syrian war, which has led to more than 250,000 deaths, displaced millions and generated a humanitarian catastrophe. But the tactic appears to be increasingly applied as President Bashar al-Assad’s forces, backed by Russian airstrikes, wage a new offensive against rebel groups.

Editor's note: This video contains graphic content. Warnings of widespread starvation are growing as pro-government forces besiege an opposition-held town in Syria. (Reuters)

The grim consequences are manifested in the vitamin-deficient mothers in blockaded areas who increasingly struggle to breast-feed, U.N. officials and aid workers warn. They say a growing number of the sick, elderly and young appear to be succumbing to otherwise preventable illnesses.

In some places, such as Madaya, people have starved to death, aid agencies say.

“We’re starving to death, women and children. We have no food,” said Dani Qappani, an activist in Moadamiyeh, an ­opposition-held town just a few miles southwest of Damascus that is under siege by government forces. In recent weeks, as many as seven people in the community of 44,000 have died because food and medicine have been cut off, said Qappani, a nom de guerre.

The tempo of the war has increased since Russia intervened with airstrikes against rebel forces in Syria late last year. Moscow’s air raids have exacerbated already dire humanitarian conditions in the country, with pro-government forces on the ground in turn tightening sieges on opposition strongholds, analysts and activists say.

Russia, a key ally of Assad, says its intervention is aimed at the Islamic State militant group, but Syrian opposition groups say the air raids have mostly targeted other rebel groups.

The sieges appear to be threatening U.N.-backed peace talks that are supposed to start in Geneva next week. Several rebel groups recently announced they would not participate in the negotiations unless the government allows humanitarian aid into areas that its forces are blockading.

Emile Hokayem, a Middle East analyst at the London-based International Institute for Strategic Studies, said Assad’s forces are pressing sieges on rebel-held areas as part of an attempt to seize as much key territory as possible ahead of the Geneva talks. Sieges are part of the government’s long-running strategy to “break and expel populations that are not loyal,” he said.

In general, U.N. officials and aid workers have increasingly expressed alarm about residents who are cut off from food and medicine by belligerents on both sides of the conflict, an age-old war tactic that is a violation of international law.

According to the United Nations, about 400,000 people are besieged in 15 locations in Syria. The world body defines an area as under siege if it is “surrounded by armed actors with the sustained effect that humanitarian assistance cannot regularly enter and civilians, the sick and wounded, cannot regularly exit the area.”

Opposition activists in Syria accuse the United Nations of playing down the number of people living under siege, excluding in its figures some areas that are cut off by government forces. Senior U.N. officials have denied the accusation.

Hassan Hassan, a Syria analyst based in Washington, said government sieges tend to be harsher and affect a far larger number of people than rebel-imposed ones. Furthermore, he said, Assad’s forces have aircraft, which rebels lack, to bomb areas it is besieging and airlift aid to loyal populations that are surrounded by opposition fighters.

Madaya, a town of more than 20,000 people, has been blockaded by government forces and allied fighters from Lebanon’s Hezbollah militia since the summer, causing more than two dozen people to die of starvation, aid workers say. A U.N.-backed agreement recently allowed humanitarian aid into the town.

In Moadamiyeh, which is not classified by the United Nations as besieged, residents and activists say government forces have completely halted the flow of food, medicine and people for the past month. A shaky truce with local rebels broke down as government forces increased attacks to capture nearby opposition-held areas.

Activists say five children, a woman and an elderly man have died of starvation-related causes since the siege was tightened in December. Like in Madaya, the activists said, Moadamiyeh residents face soaring food prices — two pounds of rice now costs about $20 or more.

“My family is living on making soup with some grass and pepper to survive,” said Majed, 22, an activist in Moadamiyeh who gave only his first name because of concerns for his safety.

Elizabeth Hoff, a World Health Organization (WHO) representative in Syria, said doctors in Moadamiyeh are warning that women are increasingly struggling to breastfeed because of a lack of nutrients. “This is a sign that you might find severe malnutrition cases, like in Madaya,” Hoff said.

WHO has been unable to verify claims of starvation deaths because the government has denied the organization’s requests since June to enter Moadamiyeh, she said.

Conditions are also difficult in areas besieged by opposition forces, such as the areas of Deir al-Zour that are surrounded by the Islamic State, which controls vast territory in Syria and Iraq. But activists from the city also accuse the Assad government of exploiting the misery of residents who face brutal attacks by the militant group, highlighting perhaps the unexpected difficulties of those who live under blockade.

Government air drops of food aid are insufficient and confiscated by officials, who then sell the food to desperate residents for exorbitant prices, said Jalal al-Hamad, director of Justice for Life in Deir al-Zour, a monitoring group that has activists in the city. To flee the area, government officials charge hefty fees that most residents are unable to pay, he said.

“People in government neighborhoods are in reality under siege by two groups: ISIS and the Assad regime,” said Hamad, a native of the city who spoke by Skype from Turkey.

“It’s a disaster.”

Suzan Haidamous contributed to this report.

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