(CNN) -- Syrian opposition groups met Monday in Cairo, Egypt, trying to find common ground as the violence continued in Syria and spilled over into neighboring Lebanon.
Syrian government forces shelled several villages with artillery and mortar fire Monday, while troops stormed others, the London-based Syrian Observatory for Human Rights said. The group said the town of Kafar Shams had been under siege for nine days, with all utilities cut off.
They were the latest examples in a pattern of escalating violence that led U.N. High Commissioner for Human Rights Navi Pillay on Monday to reiterate her call to refer the situation in Syria to the International Criminal Court.
"I believe the evidence points the commission of crimes against humanity," she told reporters after briefing the U.N. Security Council.
She cited allegations such as indiscriminate shelling, arbitrary detention and attacks on hospitals by government forces and the killing by opposition forces of suspected government informants and collaborators.
Fresh mortar shelling fell near an elementary school in Madyara, the opposition Local Coordination Committees of Syria said. Across Syria, 114 people were killed Monday, the group said.
The official Syrian Arab News Agency said troops clashed with what it calls "terrorist groups" in Deir Ezzor, killing an unspecified number of fighters and destroying a car outfitted with a machine gun. An attack on a gas pipeline in Deir Ezzor also resulted in the release of "large amounts of gas," the news agency reported.
The Syrian Observatory said it couldn't document casualties in many areas because of the fighting and poor communications. At least 109 people, including 81 civilians, died Sunday in fighting, the group said.
CNN cannot independently confirm the reports of casualties or violence because Syria restricts access by international journalists.
On the Syrian border with Lebanon, a rocket attack launched from Lebanon injured two people, the Lebanese National News Agency reported.
The agency said Syrian troops later entered the Lebanese post in Bakeyaa, captured two members of Lebanese forces, took them to Syrian territory and then released them.
Lebanon's directorate general of public security will investigate, the news agency said.
Also, Turkish officials revealed Monday that they had scrambled jet fighters Sunday to track Syrian helicopters flying near the border between the two countries. It was the second straight day Turkish officials sent jets to intercept Syrian helicopters closing in on the border, according to the Turkish armed forces.
The two-day opposition group meeting in Cairo comes after world leaders heralded a new plan over the weekend to end the crisis in Syria; the agreement between typically sparring countries netted both optimism and doubt.
The latest international plan for Syria, backed by Russia and China as well as the West, calls for a transitional government as a step toward ending 16 months of daily bloodshed. Unlike many Western countries, Russia and China have not explicitly called for Syrian President Bashar al-Assad to step down.
But U.S. Secretary of State Hillary Clinton conceded the plan, forged Sunday in Geneva, Switzerland, might not work.
"There is no guarantee that we are going to be successful. I just hate to say that," Clinton told CNN.
But she expressed optimism that the new agreement would help ease al-Assad out of power, saying the Syrian president and his inner circle would be excluded from any transitional government.
According to the agreement, the transitional government "could include members of the present government and the opposition and other groups and shall be formed on the basis of mutual consent."
Both sides have to agree on the membership of the interim body, and Clinton said there was "no way anyone in the opposition would ever consent to Assad or his inside regime cronies with blood on their hands being on any transitional governing body."
"Assad will not be part of it," she said in an interview in Geneva after the deal was hammered out.
But opposition activists slammed the agreement, saying it left open the possibility that al-Assad would remain in power.
"The new agreement provides vague language which is open to interpretation," the opposition Local Coordination Committees of Syria said in a statement Sunday. "This provides yet another opportunity for the regime's thugs to play their favorite game in utilizing time in order to stop the popular Syrian revolution and extinguish it with violence and massacres across Syria."
Russia's foreign minister will meet with leaders of the Syrian opposition during the group's visit to Moscow, the state-run Itar-Tass news agency reported Monday.
The Syrian National Council delegation could arrive in Moscow as early as Wednesday and may meet with Foreign Minister Sergey Lavrov on July 10, Itar-Tass reported, citing Deputy Foreign Minister Mikhail Bogdanov.
The Russians have also invited the U.N. special envoy on Syria, Kofi Annan, to visit in mid-July, Itar-Tass reported.
"Our task is to actively work with all parties," Itar-Tass quoted Bogdanov as saying.
Clinton said the Russians, who have long been al-Assad's most steadfast supporters, had finally decided to back a transition away from his rule.
"They have committed to trying," she said. "But they also admitted that they may or may not have enough leverage to convince not just one man, but a family and a regime that their time is over."
Russia, widely viewed as a key ally to the Syrian regime, said the agreement should not be interpreted as outside powers imposing a transitional government on the Syrians. That process must come from inside Syria, Lavrov said.
Clinton said the Security Council should endorse the plan, thus allowing the possibility of sanctions against Syria if the requirements aren't met.
But for Syrians living amid the violence, the reports of carnage never stop.
June was a particularly gruesome month, with 2,386 people killed, opposition activists said.
More than 14,000 people have been killed since the conflict began in March 2011; half of them were slaughtered in the past four months, the LCC said. The United Nations puts the death toll at more than 10,000.
The unrest has also spilled across borders, with thousands of refugees fleeing to Turkey and violence erupting on the border between Syria and Lebanon.
CNN's Jill Dougherty, Salma Abdelaziz and Holly Yan contributed to this report.