A mobile clinic with medics on board has been sent to the besieged Syrian town of Madaya that has become a symbol of civilian suffering, the World Health Organization said Friday.

The unit was dispatched by the UN agency and Syrian Arab Red Crescent to treat residents hit by malnutrition in the rebel-held town of 40,000 besieged by pro-government forces for the past six months, said Rana Sidani, a WHO regional official.

A convoy of 44 aid trucks loaded with food and medicine on Thursday entered Madaya -- where the United Nations says hardships are the worst seen in Syria's nearly five-year war.

Relief workers examined 350 residents of the town, located around 40 kilometres (25 miles) from the Syrian capital, and found multiple cases of severe malnutrition, Sidani told AFP.

A first convoy was allowed to enter Madaya on Monday after reports that more than two dozen inhabitants have starved to death since December sparked international alarm.