The United Nations plans to carry out a "vigorous," independent investigation into an attack on an aid convoy in Syria this week that killed 21 people, UN Secretary General Ban Ki-moon said Wednesday.
During a high-level briefing at the UN Security Council, Ban told world leaders that the UN would investigate the incident on Monday in Aleppo that led to the suspension of its aid operations.
"I am looking at options for vigorously investigating this and other similar atrocities against civilians," Ban said.
The US has blamed Russia for the attack; the government in Moscow and its allies in Damascus have denied they were behind the deaths, and said there was no evidence of an airstrike.
Ban also told the council that it was at a "make or break moment" to solve the Syrian crisis.
"I challenge everyone to use their influence now to restore a cessation of hostilities, enable humanitarian assistance everywhere it is needed, and support the United Nations in charting a political path for the Syrians to negotiate a way out of the hell in which they are trapped.”
Violence has surged in Syria in the past few days, pushing a ceasefire, brokered by the United States and Russia, to collapse.
At least 13 people, including three children, were killed on Wednesday in a bombardment by unidentified jets on a rebel-held town in the north-western province of Idlib, a monitoring group reported.
The Syrian Observatory for Human Rights added that dozens of houses were also destroyed in the raids on Khan Shaikhoun in Idlib.
Hours earlier, four medical staff manning a volunteer group were reportedly killed in an airstrike in Aleppo.
The International Union for Medical care and Relief Organizations (UOSSM) said that four of its members were killed and a nurse seriously injured in the strike that hit the group’s mobile medical unit in Aleppo’s Khan Touman late Tuesday.
An initial UOSSM report said that two nurses, two ambulance drivers and 10 patients were killed in the late Tuesday attack on the facility
"This is the worst day for me since I joined UOSSM," the group's chief executive Zaidoun Zoabi told dpa by phone.
"Two days ago, it was a humanitarian convoy. Today it is us," he added.
A UOSSM spokeswoman said that the group's mobile team was called in Khan Touman late Tuesday to rescue people from an earlier airstrike and when they arrived, another airstrike took place.
Founded in 2012, UOSSM is a grouping of humanitarian, non-governmental and medical organizations from the US, Canada, Britain, France, Germany, the Netherlands, Switzerland, and Turkey.
The Syrian opposition National Coalition on Wednesday blamed the collapse of the truce, which went into effect on September 12, on Russia, a key ally of Syrian President Bashar al-Assad.
"The latest air bombardment is a continuation of a series of criminal operations pursued by Russia to subdue the Syrian revolution and force [the opposition] to accept the Russian terms to save the al-Assad regime," the West-backed coalition said in a statement.
At least 300,000 people have been killed in Syria's conflict since it started in March 2011, the Observatory estimated last week.