| The air strike came a day after an attack on an aid convoy in nearby Urum al-Kubra |
An air strike on a clinic near Aleppo has killed four employees of an international medical aid agency, the group says.
The attack came a day after an aid convoy was targeted in a deadly attack nearby. The US said it holds Russia responsible for Monday's attack, which destroyed 18 lorries, killed about 20 civilians and has been described as a possible war crime.
But Russia strongly denied involvement of its own or Syrian planes, and said the incident was caused by fire on the ground and not by an air strike. The two successive attacks were "not a coincidence," UOSSM CEO Dr Zaydoun al Zoubi told the BBC.
"Somebody is trying to tell us humanitarian workers are not welcome in Syria, that we are a target, that we will be killed," he said.
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Buried under rubble
It is unclear who carried out the attack on the medical centre in the rebel-held town of Khan Touman late Tuesday night local time.The Syrian Observatory said either Syrian or Russian warplanes were responsible, Reuters news agency reports.
The strike hit a medical triage point, and killed two ambulance drivers and two nurses who had arrived to transport wounded patients to a more advanced medical facility, UOSSM said in a statement (in French).
Another nurse remains in a critical condition and the medical centre was completely destroyed. More victims are feared buried under the rubble.
The rebels killed were from Jaish al-Fatah, an Islamist group not officially part of the Western-backed alliance but one that works alongside the Free Syrian Army, the BBC's James Longman in Beirut reports.