Linda Tom a spokeswoman with the UN's Office for the Coordination of Humanitarian Affairs (OCHA) confirmed new aid deliveries were planned for Madaya where more than two dozen people are thought to have died from lack of food and two other towns.

"We are planning operations to Madaya Fuaa and Kafraya on Thursday which will be followed by a third delivery in the following days" she said on Wednesday.

She added that assistance for a fourth town Zabadani was being planned for a later date.

Badly needed supplies entered the three towns on Monday.

It was the first aid to reach inhabitants for four months and came after international concern about the situation in Madaya.

The town along with neighbouring Zabadani in Damascus province are under government siege and Madaya residents have also reportedly died after stepping on landmines or being shot by snipers while trying to leave in search of food.

Government-held Fuaa and Kafraya in Syria's northwestern Idlib province are under rebel siege and are reportedly suffering shortages of food and medicine though the regime has been able to airdrop some supplies to the towns.

On Wednesday the Syrian Observatory for Human Rights a Britain-based monitor said a child had died in Fuaa because of lack of medical treatment.

Tom said Thursday's planned convoy would take in "food health supplies and non-food items including items for winter like blankets to complement the initial delivery of humanitarian aid."

She said it remained "essential" to get medical teams into Madaya "to examine patients to determine their condition."

"Our priority is also to bring in mobile clinics to immediately provide medical care to those who can be treated in Madaya" she added.

But it was not immediately clear if that would be possible on Thursday.

Aid officials who accompanied Monday's convoy confirmed cases of malnutrition inside Madaya.

"We saw a number of people that were clearly malnourished especially children and heard that hundreds of others were in urgent need of medical care that could not be provided" Tom said.

She added that the Word Health Organization had "urgently requested authorisation to bring in medical teams to attend to patients."

Madaya Zabadani Fuaa and Kafraya were part of a rare deal in late September to halt fighting and deliver aid to trapped residents.

But only a single aid delivery had taken place before this week and residents in Madaya in particular reported dire conditions.

The International Committee of the Red Cross on Wednesday urged the immediate lifting of all sieges in Syria saying more than 400000 Syrians were living in besieged areas.

More than 260000 people have died in Syria since the conflict began with anti-government protests in March 2011.