BEIRUT: 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 has 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 250000 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.

The grim consequences are manifesting in the vitamin-deficient mothers in blockaded areas who increasingly struggle to breastfeed U.N. officials and aid workers warn. A growing number of sick elderly and young they say 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 that is also besieged by government forces just a few miles southwest of Damascus. In recent weeks as many as seven people in the community of 44000 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 rebel groups.

The sieges appear to be threatening U.N.-backed peace talks that are supposed to be held in Geneva next week. Last week several rebel groups 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 400000 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 20000 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 from 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 the Justice for Life in Deir al-Zour a monitoring group that has activists in the city. To flee the area government officials also 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.)