Doctors Without Borders, known by its French acronym MSF, said it was evacuating medics and patients from the Al Salamah in northern Syria as the Islamic State militants neared.
It said a basic team would remain to help the ill and wounded and that around 100,000 people were under threat from the IS offensive.
"MSF has had to evacuate most patients and staff from our hospital as frontlines have come too close," Pablo Marco, MSF operations manager for the Middle East, said in a statement.
"We are terribly concerned about the fate of our hospital and our patients, and about the estimated 100,000 people trapped between the Turkish border and active frontlines. There is nowhere for people to flee to as the fighting gets closer," Marco added.
In a statement, IS claimed to have taken control of seven villages from the Free Syrian Army and "apostate" fighters.
In Kaljibrin, there were reports that militants had publicly executed rebel fighters and their families, including women and children, in a main square.
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Militants said it had seized American-made weapons from "US-vetted" groups in the advance, although it was impossible to verify the claim.
The IS offensive has split rebel-held territory in northern Aleppo governorate into two, leaving a thin sliver linking the city of Azaz to the Turkish border and town of Marea, bordered on the other side by Kurdish groups.
Syrian rebel factions in the area, which includes the border crossing of Bab al-Salama, have also come under fire from pro-government forces and the predominantly Kurdish Syrian Democratic Forces in recent months.
A London-based Syrian Observatory for Human Rights said Friday's advance also effectively cut off a key supply route between Azaz and Marea, another opposition stronghold.
Both Azaz and the Bab al-Salama crossing have been a lifeline for the opposition since the town fell into rebel hands in 2012 but are being threatened by Russian air strikes and fighting.
MSF and other aid organisations warned earlier this month that the humanitarian situation for over 100,000 people trapped in the Azaz rebel-held pocket was critical.
Staffan de Mistura, the UN envoy for Syria, said he plans for a resumption of peace talks "as soon as feasible" between the Government and opposition but expects that it will "certainly not" come within the next two to three weeks.
IS and the Al Qaeda linked Jabhat al-Nusra are excluded from negotiations, which were suspended last month between Bashar al-Assad's government and other rebels
--IANS
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