New York - The deadly attack on a UN aid convoy near the Syrian city of Aleppo became a grim reminder to diplomats gathered for this year's United Nations General Assembly (UNGA) of the challenges facing humanitarian aid agencies.

The #NotATarget stand-in, organised by UN staffers for three days, drew attention to what was on the minds of the aid community attending the event.

Although the UN's humanitarian aid agency said it had resumed aid delivery on Thursday, news of warplanes bombing aid trucks during a fragile week-long ceasefire - an attack that killed at least 20 people - has brought the topic to the fore this week.

"The attack on the convoys was egregious," said Jason Cone, executive director for Doctors Without Borders (MSF), which supplies a network of 150 health centres and clinics in different parts of Syria.

"All the parties to the conflict need to accept that aid needs to come in - it shouldn't require ceasefires for this to happen," he said.

The UN's refugee agency estimates that 13.5 million of Syria's population of nearly 18 million are in need of humanitarian assistance. Delivering aid in the country is "incredibly difficult and dangerous", Cone said.

"Every time we try and bring in assistance, it's in a very clandestine way," he added. This is how MSF has been getting aid into Aleppo to help the 250,000 people trapped there.

'Chilling effect'

Unlike in other countries, MSF does not provide coordinates for their clinics to Syrian officials and combatants, "because those hospitals have been targeted as part of the war strategy".

"In 2016, we had 31 attacks on 19 MSF facilities - it absolutely has a chilling effect. While we're running large operations in Syria and around Syria in places like Lebanon, Turkey and Iraq, we're nowhere near meeting the needs - nobody is," said Cone.

Selim Salamah, a refugee from Syria and director of the Palestinian League for Human Rights, said the UN "should have led more efforts" way before the attack on the convoy in negotiating humanitarian access.

"We will see little outrage as most members of [this] convoy were Syrians - no foreigners' lives were lost to cause an international anger," he added.

Four in five Yemenis in desperate need of humanitarian aid

US officials have blamed the strike on Russia, the key ally of Syrian President Bashar al-Assad. Moscow has rejected the allegations that Russian or Syrian warplanes carried out the attack.

Syria is not the only place where aid delivery is a challenge. Places like South Sudan and Yemen have also proved vexing, largely because of the number of non-state armed groups with whom any kind of safe passage for convoys of goods has to be negotiated.

Jehanne Henry, senior researcher in Human Rights Watch's Africa division, told Al Jazeera that how and if an aid convoy can get in largely depends on the parties involved.

"Some organisations have a higher threshold for risk," she said. "But when big attacks on aid groups happen, it certainly has huge, very far-reaching consequences."

As an example, Henry mentioned the July attack on aid workers at a compound outside Juba, the capital of South Sudan. Aid organisations all evacuated their staff and have only recently come back, Henry said.

"When aid groups leave and when operations are suspended, we know that it affects the civilian population. The insecurity, the limits in the reach of aid groups ... at the end of the day, it's the civilians, it's the villagers who suffer," she added.

Worldwide, 246 million children live in areas affected by conflict - 12 to 15 million of them in areas actively involved in war - and 28 million children have been displaced by conflict. 

"The numbers are mind-boggling," said Saudamini Siegrist, senior adviser for child protection emergencies at the UN agency for children (UNICEF).

She told Al Jazeera that while the tactic of blocking access to humanitarian aid is not a new thing, aid agencies have been facing increasing difficulties in accessing the most vulnerable populations.

"We have a lot of experience in this area, and I would say that we will not be deterred," said Siegrist.

But, she added, being cut off from aid, combined with not having access to education, will have short and long-term consequences for children.

"It will have a crushing impact on the lives of children ... and recovery takes time," she said. "There's no quick fix."

Source: Al Jazeera