BEIRUT -- Desperate for food and basic medicines, many of the besieged and bombarded Syrian civilians in Damascus' eastern suburbs of Ghouta awaited Monday as a 46-truck convoy organized by the United Nations and key aid agencies began entering the rebel-held enclave. The U.N.'s humanitarian office said the convoy with health and nutrition supplies, along with food for 27,500 people in need, entered the town of Douma in the besieged eastern Ghouta.

In a Twitter posting, however, it said that many life-saving health supplies were not allowed to be loaded.

"This delivery of assistance is a first positive step that would lessen the suffering of the civilians in the area," said Ingy Sedky, a spokeswoman for the International Committee of the Red Cross in Damascus.

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"However, more needs to be done in the coming period," she added. "A one-time aid delivery will never be enough to fulfil the needs. Repeated and continuous access to Eastern Ghouta by humanitarian organizations is a must."

Sedky said Monday's delivery includes 5,500 food and flour bags enough for 27,500 people, in addition to wheat flour, medical and surgical items.

Pawel Krzysiek of the International Committee of the Red Cross said earlier that the inter-agency convoy had arrived in Wafideen, a key crossing point set up by the Syrian government for civilians wishing to leave eastern Ghouta and also for aid to enter the enclave.

We are on the move towards #EasternGhouta. 46-truck convoy of @ICRC_sy @SYRedCrescent and @UN just arrived in Wafideen camp. Feels like racing with tim pic.twitter.com/rwjxtHuReq — Pawel Krzysiek (@PKrzysiekICRC) March 5, 2018

Activist groups said the convoy had begun crossing into the besieged area, marking the first entry of aid materials in weeks.

"Feels like racing with time," Krzysiek said in a tweet before crossing. Eastern Ghouta, home to some 400,000 people, has been under a crippling siege and daily bombardment for months. More than 600 civilians have been killed in the last two weeks alone

U.N. aid official Ali Al-Za'tari told journalists as he waited in one of the vehicles that the convoy had hoped "to enter without shelling sounds, because there must be respect of the ceasefire, especially that this is a humanitarian convoy heading to a big number of civilians to help civilians."

The U.N.'s office for humanitarian affairs and the World Food Program says Monday's convoy to the town of Douma in eastern Ghouta will consist of 46 truckloads of health and nutrition supplies, along with food for 27,500 people in need. U.N. officials had said lack of approvals and consensus among the warring parties, as well as the limited duration of a daily, five-hour Russian-ordered humanitarian pause, had made aid delivery impossible.

The Syrian government, meanwhile, says it has achieved "significant" progress in its ongoing military operation in rebel-held suburbs east of Damascus, seizing around 36 percent of the total area held by different armed groups.

Syria's Central Military Media says troops are continuing their advance from the east and are only 3 kilometers, or 1.8 miles, from meeting troops advancing from the west, which would achieve the partitioning of eastern Ghouta into two parts.

Monday's announcement comes a day after troops recaptured control over the town of Nashabiyah and a number of villages and farms in eastern Ghouta in the largest advances since the government's wide-scale operation began last month.