A first convoy of humanitarian aid crossed into Syria from Turkey on Thursday under a new UN-authorized plan to send relief without Damascus' approval.
"Nine trucks crossed at Bab Al-Salam into Syria this morning," said Amanda Pitt of the UN Office for the Coordination of Humanitarian Affairs (OCHA).
"They were carrying food, shelter, water and sanitation supplies," she told AFP.
The UN Security Council last week adopted a resolution authorizing the cross-border aid deliveries without the consent of the Damascus regime, to help more than one million civilians.
More relief shipments are due to leave from three other crossing points -- Bab Al-Hawa in Turkey, Al-Ramtha in Jordan and Al-Yarubiyah in Iraq -- in the coming months.
More than 10.8 million Syrians are in need of aid, according to UN officials, who have repeatedly accused Damascus of impeding deliveries of life-saving supplies.
International aid agencies have hailed the UN cross-border aid program as a potential lifeline for millions of Syrian civilians trapped in the crossfires of the war, now in its fourth year.
Attacks on hospitals
UN Secretary General Ban Ki-moon said in a report to the Security Council on Thursday that Syrian government forces were stepping up their attacks on hospitals and clinics, and that all sides were blocking aid deliveries as a "tactic of war."
Signup to our newsletter and follow us on Facebook and Twitter!
Syrian rebel groups including Islamic State fighters who control all access to routes in eastern areas are blocking humanitarian deliveries with some 711,000 civilians affected, the report said.
Damascus is denying approval of medicines and surgical equipment to hard-to-reach areas, with 24,000 people deprived for six months of life-saving treatment in Madamiyet ElSham, near the capital, it added.
"The parties have continued to obstruct humanitarian assistance to those most in need and to withhold consent for operations in a completely arbitrary manner as a tactic of war," he said.
In June alone, there were 12 attacks on medical facilities, the second highest number since December 2012 and all were committed by government forces, the report said, quoting Physicians for Human Rights.
Ban accused both government forces and rebel fighters of increasingly targeting vital services such as water stations and electric cables, compounding the humanitarian crisis.
Under the new UN plan, which is valid for six months, convoys will be monitored by UN teams who will simply inform the Syrian government but will not seek approval from Damascus for the shipments.
The war in Syria has left more than 170,000 dead, with diplomatic efforts to revive peace talks at a standstill.
Ban has named Italian-Swedish diplomat Staffan de Mistura to be his new UN mediator after the highly-regarded Lakhdar Brahimi resigned in May over the collapse of peace talks.
De Mistura has yet to announce how he plans to lead his peace mission.