Thousands of people in Syria's besieged villages and towns, particularly Madaya, are suspected to have starved to death, United Nations Human Rights Council (UNHRC) chief Zeid Ra'ad Al Hussein reportedly said Monday at the council's 31st annual session.

Human rights have been "violated shockingly" in Syria, where a civil war started five years ago, the UNHRC commander said. The UN will on Monday send humanitarian aids to the areas under the siege of the President Bashar al-Assad's government as well as rebel groups, which accepted the terms of a ceasefire that came into effect Friday midnight.

"The deliberate starvation of people is unequivocally forbidden as a weapon of warfare. By extension, so are sieges, which deprive civilians of essential goods such as food... Thousands of people may have starved to death," Agence-France Presse quoted Hussein as saying.

"Neighbourhoods, schools and packed marketplaces have been hit by tens of thousands of air strikes, thousands of barrel bombs have been thrown out of helicopters onto streets and homes," he said, adding some parties "are targeting medical units deliberately, or with reckless disregard."

As many as 480,000 people "currently trapped in besieged towns and villages in Syria — and have been, in some cases for years" are stranded in a desperate situation, Hussein said, adding that the situation looks to be much more distressing in Madaya.

United States Ambassador to the United Nations Samantha Power had in January said that over 400 people "on the brink of death" need to be evacuated from Madaya, where according to reports several people were on the verge of starvation.

Last year, in December, the Syrian Observatory for Human Rights said that at least 40,000 civilians in Madaya were facing acute shortage of food, medicine and other basic supplies due to the siege by the Syrian government and Hezbollah militants.

The situation is likely to improve with the enforcement of a ceasefire agreement that was proposed by the US and Russia this month. The UN targets to deliver supplies to 154,000 more people in the besieged towns and villages over the next five days.