A Syrian man carries a wounded girl after an explosion targeted a military bus on June 8, 2012.
- Twenty people are killed and dozens wounded in shelling in Daraa, the opposition says
- Syria blames killings on terrorists while rebels say it was regime forces
- U.N. monitors say there are signs of an attack in the village
(CNN) -- The opposition accused Syrian forces of shelling a neighborhood and detaining doctors who aided the wounded as world leaders scrambled to find a solution to end the relentless violence.
The reports of violence come as President Bashar al-Assad's government and opposition forces blamed each other for a massacre this week in the village of Qubeir, where U.N. observers discovered signs of an attack.
At least 20 people were killed and dozens wounded in shelling Saturday morning in the southern city of Daraa, said the Local Coordination Committees of Syria, an opposition group.
Among the dead, according to the group, were women and children killed in clashes between Syrian forces and rebel fighters in the area.
"Several doctors have been detained to prevent them from aiding the wounded amid a state of panic among residents due to the abuses regime forces are committing against the people there," the group said.
CNN cannot independently confirm reports of casualties or violence as the Syrian government has restricted access by international journalists.
International leaders accuse al-Assad of failing to comply with a peace plan brokered by Kofi Annan, a special envoy on Syria for the United Nations and the Arab League.
Annan, who has been meeting with U.N. officials, is trying to salvage the peace plan to end the 15-month anti-government uprising.
As part of his peace plan, U.N. observers have been in Syria to monitor whether both sides are abiding by the agreement.
On Friday, the observers made it to the site of what the opposition called a massacre Wednesday in the village of Qubeir, near Hama, after they were denied access a day earlier by government forces and civilians in the area, said Sausan Ghosheh, spokeswoman for the U.N. Supervision Mission in Syria.
Observers found signs of an attack in the village, including some homes damaged by rockets, grenades and a range of other weapons, Ghosheh said. There also were tracks left by armored fighting vehicles that were visible in the vicinity, she said.
Ghosheh said the U.N. team found the village empty, and "the observers were not able to talk to anyone who witnessed Wednesday's horrific tragedy."
She said that the circumstances surrounding this crime "are still unclear. The number and names of those killed are still not confirmed."
The LCC alleges that at least 78 people were killed in Qubeir, while the Syrian government blamed terrorists for the attack that it says killed only nine people.
The state-run Syrian Arab News Agency discounted the opposition account of what happened in Qubeir, citing in its report a witness from the village who claimed to have seen the assault -- by "armed terrorists groups."
The government's claim sharply contrasts with the opposition, who accused government forces of shelling the village for an hour before militias on foot turned AK-47 rifles on people, some at close range, or slashed them with knives. Some residents suspected the Shabiha, armed gangs that work as freelancers for the government, the opposition said.
A video purporting to show the carnage, was posted on YouTube. The video did not show who carried out the actual killings. CNN could not independently verify its authenticity.
Though China condemned the violence Friday, its leader along with representatives of Russia and four Central Asian nations signed a joint declaration rejecting armed intervention in Syria and reiterating support for Annan's peace plan.
Frustrated world leaders warned that Syria is engaging in crimes against humanity and drifting closer to civil war.
"The danger of full-scale civil war is imminent and real, with catastrophic consequences for Syria and the region," U.N. Secretary-General Ban Ki-moon said after marathon talks Thursday on Syria.
CNN's Hamdi Alkhshali and Journalist Rob Alhenawi contributed to this report
