In September, a ceasefire agreement led to the setting up of a demilitarized zone between Government forces and rebel-held parts of Idleb, which is the last part of the country still largely in opposition hands, and home to around three million civilians, many displaced from elsewhere.

Mark Cutts said he was “appalled and outraged by the news of the abduction and killing of an aid worker”, explaining that the duty to ensure humanitarians can do their job free from danger, falls on the parties to the conflict. Such attacks only perpetuate the crisis that aid teams are supposed to help alleviate.

“Such acts of violence put into jeopardy the continuation of a humanitarian operation that is providing a vital lifeline for millions of people in Syria”, he said.

Cutts highlighted that throughout the near eight-year Syrian conflict, aid workers and assistance professionals have been subjected to violence, and that hundreds “have been killed or injured during the conflict.”

“Violence, threats and intimidation” have marred the progress of humanitarian work, he said, including numerous abductions, and dozens of conflict-related slayings were reported last year alone.

The latest figures from 2018 on aid worker security show Syria to be the third most lethal country for those on the job, behind South Sudan and Afghanistan.“In the northwest there has been a disturbing trend in recent months of increased kidnappings, extortion and attacks affecting health workers and humanitarian staff,” Cutts said.

Though fewer attacks were reported from Syria, the use of aerial bombardment character to the country’s violence resulted in more aid workers killed per incident, with most attacks taking place in areas of severely constrained access for aid organisations, according to the 2018 Aid Worker Security Database.

Overall last year, 139 aid workers were killed in different parts of the world, another 102 wounded, and 72 kidnapped in the line of duty.

As Syria’s war continues to rage on, more than 13 million people there need humanitarian assistance, and their lives will be increasingly under threat if aid workers are hindered from performing their duties.

“These acts of violence affect the individuals, their families, colleagues, and communities that these humanitarian workers serve and may deprive these vulnerable people of services they rely on to survive”,  Cutts said.

“I call on all parties to the conflict to take the necessary measures to prevent any further attacks on humanitarian workers and to ensure their protection at all times,” he added.