By Mariam Karouny

BEIRUT (Reuters) -- Trucks loaded with humanitarian aid entered four besieged Syrian towns and villages as part of a deal agreed last month between Syria's warring sides with U.N. help, local sources and the International Committee of the Red Cross (ICRC) said on Sunday.

A total of eight trucks carrying food and medical aid entered the Shi'ite towns of Kefraya and al-Foua, under rebel siege in Idlib province in northwest Syria.

Simultaneously, trucks arrived in the towns of Madaya and Zabadani, where insurgents are holed up in a mostly government-held area near the Lebanese border. More trucks were heading for the nearby areas of Buqain and Saraghaya, bringing the total for the rebel-held areas to 23.

The International Committee of the Red Cross said its staff had entered Zabadani late on Sunday. “They are doing the distribution of medical supplies to treat the wounded,” said spokeswoman Dibeh Fakhr.

The Syrian Arab Red Crescent and U.N. agencies were involved in a parallel aid operation in Kefraya and al-Foua, where they were distributing food and non-food supplies, she said.

The Syrian Observatory for Human Rights, which monitors the war through a wide network of sources, confirmed that trucks had reached Madaya and al-Foua.

Activists said they were expecting 5,500 meal packages to go to Madaya, 2,100 to Saraghaya, and 100 to Zabadani.

Thousands of civilians are still living in Madaya, including hundreds who escaped the fighting in Zabadani.

The supplies were part of a bigger deal reached under U.N. auspices in September in talks backed by Iran, which supports the Syrian government, and Turkey, which supports the rebels.

The initial deal included a six-month ceasefire in these areas and the evacuation of wounded rebels from Zabadani, which was the scene of fierce fighting between the Syrian army and Lebanese Hezbollah fighters on one side and insurgents including the Ahrar al-Sham group, which led the talks on the rebel side.

The United Nations had earlier this month put back the deliveries because of intense fighting elsewhere in Syria.

But the arrival of the trucks, together with the fact that a ceasefire in the areas is holding, offers a rare chance of success for foreign-brokered diplomacy in a conflict now in its fifth year, in which at least 250,000 have been killed.

Thousands of civilians in the Shi'ite villages of Foua and Kefraya are also meant to be evacuated under the deal.