GENEVA — A UN-appointed commission is collecting evidence on 20 massacres in Syria, a reflection of the civil war’s growing brutality, the panel’s chairman said Monday.
The massacres include three in the central city of Homs since December, commission chairman Paulo Sergio Pinheiro said.
The destructive standoff between President Bashar Assad’s regime and antigovernment rebels is fueling a spike in the intentional mass killings of civilians by both sides, in violation of international humanitarian law. There has also been an increase in the recruitment of child soldiers by the two sides, the panel said.
‘‘There are no more enclaves of stability in Syria today, and the civilian space is almost completely eroded,’’ Pinheiro told reporters after giving an update on Syria to the United Nation’s top human rights body.
In fighting Monday, mortar shells struck a predominantly Christian neighborhood and a football stadium at game time in Damascus, killing six civilians and wounding at least 24. The attacks appeared to be an escalating campaign by rebels to sow fear in the Syrian capital.
Opposition fighters stepped up mortar attacks on Damascus in recent weeks, striking deeper into the heart of the city.
Rebel fighters tried in the past to establish bridgeheads in Damascus but were pushed back to the suburbs by regime forces. Recent rebel mortar attacks on the city signal a new tactic in trying to loosen Assad’s grip on his main stronghold.
There was no claim of responsibility for Monday’s mortar attacks and it was not clear whether the Christian neighborhood and the football stadium were targeted or were struck by stray shells.
Pinheiro and three other members of the special UN commission began their work in August 2011 after being appointed by the 47-nation UN Human Rights Council.
In its report, the panel described Syria as a ‘‘marketplace of war,’’ opening the door to rampant corruption and extortion.
Another of the most alarming features, it added, has been the use of medical care as ‘‘a tactic of war,’’ with medical personnel and hospitals deliberately targeted and medical access denied on political and sectarian grounds.
Commission member Vitit Muntarbhorn told reporters that both sides are committing war crimes, but it appears that ‘‘government authorities have been involved more in regard to crimes against humanity.’’
The panel’s report to the Geneva-based council, covering Jan. 15 to March 3, said Syria appears condemned to ‘‘an unimaginably bleak future’’ as government forces target civilians in bakery lines and funeral processions, and anti-government rebels continue to use protected objects, such as mosques, as bases or for weapons storage.
It blamed both sides for failing to do enough to protect civilians in Syria, where 2.5 million people are internally displaced and another 1 million have fled to bordering countries as refugees.
The United Nations estimates more than 70,000 people have been killed in the Syrian civil war, which started two years ago as a popular uprising.