"Today in Syria, the abnormal is now normal," the organization, known by its French initials, MSF, said in a tweet. "The unacceptable is accepted."
On Monday, airstrikes in northern Syria hit two hospitals
and a school, killing at least 25 people, according to reports.
"It can only be considered deliberate, probably carried out by Syrian-government-led coalition that is predominantly active in the region," MSF said.
One of the hospitals hit was in Azaz in Aleppo province. Also struck in Azaz was a school housing displaced people.
'The normalization of such attacks is intolerable'
The other hospital that was hit was about 60 miles (100 kilometers) away, in Maarat al-Numan in Idlib province. Missiles struck that hospital four times in a matter of minutes, MSF said.
MSF blamed the regime of Syrian President Bashar al-Assad for the strike on one of the hospitals.
"#Idlib: At 9:00 a.m airstrikes destroyed a hospital supported by MSF," the charity tweeted. "At least 25 were killed, among them 9 medical staff &16 patients."
And the organization quoted Joanne Liu, its president, as saying, "Attacks on civilians and hospitals must stop. The normalization of such attacks is intolerable."
Fighting continues despite ceasefire plan
Meanwhile, fighting continued in Syria despite an agreement last week to pause hostilities by Friday. There were fresh reports Thursday of the Syrian army continuing at least one offensive.
And the Pentagon said Thursday that it had asked Russia to avoid striking specific areas in Syria to ensure the safety of U.S. special operations forces on the ground.
The two powers were also engaged in ongoing discussions to ensure their fighter jets did not come into contact with each other in Syrian airspace, a Pentagon spokesman said.
Operation to retake town from ISIS
The U.S.-backed Syrian Democratic Forces said they have launched an operation to wrest a key area from ISIS control.
The operation to take back Ash Shaddadi began on Tuesday, according to a statement from the group, a makeshift alliance of Kurdish and Arab fighters.
Ash Shaddadi, a strategic ISIS-held town near the Iraqi border, is at a critical road junction, sitting between Raqqa in Syria and Mosul in Iraq.
If the SDF take Ash Shaddadi, ISIS will have a logistical headache in connecting its most important cities.
Already, the forces say they now control the main road connecting Raqqa to Mosul and have seized control of the nearby Kabiba oil field, according to the London-based Syrian Observatory for Human Rights.
The observatory says the SDF have also seized control of more than 20 villages near Ash Shaddadi from ISIS.
Damascus objects to Merkel's call for no-fly zone
Syrian state media also reported the Syrian government's response to German Chancellor Angela Merkel's comments earlier in the week expressing support for the creation of a no-fly zone in northern Syria
, quoting an official who "completely rejected" the suggestion.
In an interview with German newspaper the Stuttgarter Zeitung, the German leader had said such a move could create a haven for fleeing families, and offer at least a partial solution to Europe's refugee crisis.
"(I)t would be helpful if there were areas there, where no party to the war flew bombing missions -- in other words a kind of no-fly zone," she was quoted as saying as she responded to a reporter's question about her position on exclusion zones.
But Syrian state news agency SANA quoted an official at Syria's Foreign and Expatriates Ministry as saying Merkel's request was in line with a longstanding Turkish request that would simply protect terrorist groups and allow them continue their crimes against the Syrian people.
A no-fly zone would violate Syria's sovereignty and territorial integrity, and only prolong the crisis in Syria, the official said, according to SANA.
The Syrian civil war has raged now for five years. At least a quarter of a million people are estimated to have died, and millions have fled the country, some to Turkey and others to the European Union.