(CNN) -- Claiming deaths across Syria have risen in the past month, an opposition group Friday had a message for the U.N.-backed observer mission: Implement a peace plan in order to stop the killings -- or go home.
The Syrian Observatory for Human Rights cited the shelling deaths of eight people in Daraa in its slam of the international effort.
"The monitors have played no positive role to stop the rising violence," it said.
But the head of the U.N. observer mission said the increasing violence in the country is impeding his group's work, and he urged all parties to give the observer mission a chance.
"The escalating violence is now limiting our ability to observe, to verify, to report as well as assist in local dialogue and stability projects," Maj. Gen. Robert Mood told reporters in Damascus.
Friday's death toll stood at 48, according to the opposition Local Coordination Committees of Syria, including 12 in the Damascus countryside, nine in Homs and 10 in Daraa province. The observatory said nine people died early Saturday.
The conflict has largely played out as a series of daily countering claims, with the opposition accusing government forces of indiscriminate shelling of residential neighborhoods or other such violence, while the government claims its forces are battling "armed terrorists" bent on destabilizing the government.
The deaths of eight people outside a mosque in the town of Busra al-Sham was typical of such counterclaims.
The observatory said the deaths were the result of a shell explosion. A video posted by the group shows what it calls the aftermath, bloodied bodies on a sidewalk and street. The camera operator says the carnage resulted from a Syrian army shell hitting protesters.
The state-run Syrian Arab News Agency (SANA), however, said "an armed terrorist group detonated two explosive devices" outside the mosque.
CNN cannot independently verify government and opposition claims of casualties because access to Syria by international journalists has been severely curtailed.
In Damascus, Mood briefed reporters as shells rained down on flashpoint towns and protesters took to the streets.
"Violence, over the past 10 days, has been intensifying, again willingly by both parties, with losses on both sides and significant risks to our observers," he said. The population is suffering, "and in some locations, civilians have been trapped by ongoing operations."
Mood said a peace plan put together by U.N. and Arab League envoy Kofi Annan -- which outlined an end to the violence in Syria -- is not being implemented. The observers are tasked with seeing if the government and rebels are adhering to the plan and are monitoring what was supposed to be a cease-fire, the plan's centerpiece.
"Initially, there was a lull in violence, brought about willingly by the parties, and UNSMIS (the United Nations Supervision Mission in Syria) began to engage with the local population, establishing trust and building bridges between the local authorities and opposition groups," he said.
But the lull did not last. President Bashar al-Assad's government and the opposition have accused each other of violating the six-point initiative. Mood said neither side has been willing to forge peace and there is a "push toward advancing military positions."
As part of Annan's plan, roughly 300 unarmed U.N. observers are in Syria.
This week, a U.N. official overseeing monitors in Syria described the violence as a "civil war," the first time anyone with the global body has used such language to describe the uprising.
Heavy shelling was reported in and around Homs, including hard-hit Baba Amr, according to the LCC. Shelling was also reported in Andan in the province of Aleppo.
The Syrian Observatory for Human Rights appealed to the Red Crescent and Red Cross to evacuate those wounded by shelling in Homs, particularly in the Khaldiya neighborhood. It cited a lack of water and electricity and the inability of surgeons to work in the area
Homs-based activists on Skype said they think the regime is trying to storm all neighborhoods in the city. Military movements indicate the arrival of reinforcements, they reported.
The activists said an opposition Free Syrian Army unit named the "Baba Amr brigade" claimed Wednesday it had taken over a checkpoint leading into the city. They posted video to support the claim.
The French Foreign Ministry, on its website, said it was concerned about reports of an imminent large-scale operation against Homs.
"An end must be put to the bloody repression carried out by the Syrian authorities, where there have still been dozens of deaths in recent days and the continuation is intolerable," the ministry said. "The regime of Bashar al-Assad continues to seriously violate its commitments under the Annan plan and threatens international peace and security. "
The Syrian government, meanwhile, warned of possible suicide bomb attacks against mosques in Damascus after the arrest of a man with ties to the Al Nusra Front, a group the government says has ties to al Qaeda.
SANA reported the arrest of Mohammad Houssam al-Sadaki, who it said confessed to plans to blow himself up at a central Damascus mosque.
"The terrorist confessed that supposedly there will be other terrorists who will carry out suicide attacks in a number of mosques in central Damascus during the Friday prayer," SANA reported.
Friday is typically a day of protest among anti-government groups that are calling for the ouster of al-Assad. The theme of this week's protest, according to organizers, was "total dispatch for total mobilization" -- a call for Syrians to rise up.
In the latest report of abuses, Human Rights Watch said Syrian government forces have used sexual violence to torture detained men, women and boys.
Witnesses and victims also told Human Rights Watch that soldiers and pro-government armed militias have sexually abused women and girls as young as 12 during home raids and military sweeps of residential areas.
The Syrian opposition has repeatedly called on the United Nations and world leaders to take the lead and intervene to end the escalating bloodshed, including recent massacres in Houla and Quebir and eight days of bombardment in the city of al Haffa.
World leaders have been wrangling over what to do about the conflict in Syria, leaving the U.N. Security Council at a standstill over possible action.
On one side are the United States, the European Union and much of the Arab League, which are demanding that al-Assad step down and end the violence. On the other side are Russia, China and other trade allies of Syria, which say the conflict is an internal matter that must be decided by Syrians.
The United Nations estimates that more than 10,000 people -- mostly civilians -- have been killed in Syria and tens of thousands displaced since the uprising against al-Assad began about 16 months ago. The opposition puts the toll at between 12,000 and 14,000.
Al-Assad's government moved to quash the protest movement, which quickly devolved into an armed rebellion.
CNN's Saad Abedine, Chelsea J. Carter and Joe Sterling contributed to this report.