A Syrian army helicopter hovers above a national flag bearing a portrait of Syrian President Bashar al-Assad on January 11, 2012.
- NEW: U.N. monitors are going into Tremseh Saturday to "seek verification of the facts"
- NEW: At least 35 people are killed across Syria on Saturday, opposition activists say
- A U.S. official slams Syrian President Bashar al-Assad after the Tremseh massacre
- The Syrian government blames the Tremseh incident on armed terrorist groups
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(CNN) -- Still grappling with a gruesome massacre that has outraged world leaders, Syrians endured yet another bloody day Saturday as regime forces fired from low-flying helicopters and a bombing at a state security headquarters killed at least six people, opposition activists said.
At least 35 people were killed in Saturday violence, including 10 in Homs, eight in Damascus Suburbs and seven in the town of Muhrada, in Hama province, the Local Coordination Committees of Syria said.
Another opposition group, the Syrian Observatory for Human Rights, said a car bombing targeted a state security building in Hama, and "a number of state security personnel were killed and wounded."
Syrian state-run TV said at least three civilians and a security officer were killed in Muhrada by a suicide bomber in a truck.
Farther south, the Daraa province town of Khirbet Ghazaleh came under heavy shelling and machine gun fire after the Syrian army surrounded it with tanks, the LCC said.
"Helicopters fly over the city at a low altitude with a continued siege of the city and gunfire from snipers," the opposition network said.
Meanwhile, Deir Ezzor, where six deaths are reported, is subject to intense shelling by government forces, it said, as well as fierce clashes between regime forces and the Free Syrian Army, the LCC said.
The reports of relentless violence come two days after Syrians endured what may be the single deadliest day in the 16-month crisis.
More than 200 villagers were killed in the Hama-area town of Tremseh on Thursday, the LCC said, and dozens more were killed elsewhere across the country.
A spokeswoman for the head of the U.N. Supervising Mission in Syria, Maj. Gen. Robert Mood, said a large patrol had been sent to Tremseh Saturday to assess the situation, amid widely differing accounts of what happened from opposition activists and the government.
An initial reconnaissance mission was sent Friday following assurances of a ceasefire in the area, said spokeswoman Sausan Ghosheh, but it was too late to do much.
"The patrol assessed the situation -- if there was in fact a ceasefire and our access to the town," she said. "We have sent a large integrated patrol today to seek verification of the facts."
International anger against Syrian President Bashar al-Assad has ratcheted up since the Tremseh incident, with at least one U.S. official suggesting the need for more pressure on al-Assad's regime.
"Through these repeated acts of violence against the Syrian people, President Assad has lost legitimacy to lead. It is time for him to go. It is time for the political transition that is long overdue to finally get underway," Josh Earnest, a White House spokesman, told reporters Friday.
"It certainly does build strong international support ... to continue to ramp up the pressure on Assad," he added, citing "ongoing conversations at the United Nations about additional ways that we can build some international agreement and raise the stakes even further."
Another 80 people were killed Friday, according to the LCC.
The dead include seven members of the same family who were killed when a mortar fell on their home in the city of Douma, near Damascus, opposition activists said. Activists posted an amateur video that purports to show their bodies covered with blankets and sheets while a man in mourning calls for revenge against al-Assad.
CNN cannot independently verify reports from Syria because the nation has restricted access by international journalists.
Activists in the city of Hama, meanwhile, gave a grisly account of the assault in Tremseh.
Witnesses inside the town told the activists by telephone that Syrian military forces had launched a full-scale attack against the opposition Free Syrian Army inside the town, which was surrounded by government tanks and artillery.
As the government forces rained artillery rounds into the town, a number of village residents fled their houses, going into the streets, where many of them were shot dead by the government militias, the activists told CNN.
The government painted a starkly different picture of Tremseh than that detailed by opposition groups.
The state-run Syrian Arab News Agency blamed "armed terrorist groups" for the violence. It said the government said residents called security forces for help after the terrorist groups raided the neighborhood.
Regime forces arrested some of the members of the terrorist groups and confiscated their weapons, the government said.
"Armed forces successfully dealt with the terrorists without casualties taking place among the citizens. They searched into the terrorists' dens where they found the dead bodies of a number of citizens who had been abducted and killed by the terrorist groups," SANA reported, citing a military source.
Meanwhile, many who survive the violence are caught in a precarious humanitarian situation.
The chief U.N. organization that coordinates emergency aid warned Friday that more Syrians will die if contributing nations do not follow through and fund its relief operation.
"We have run out of language to describe how it is for the civilian population," said John Ging, operations director and chairman of the Syria Humanitarian Forum for the U.N. Office for the Coordination of Humanitarian Affairs. "It is physical and it is psychological."
Humanitarian agencies in Syria are facing "an incredibly complex and dangerous situation to develop networks to be able to deliver to the areas that have been affected by the conflict," he said.
Though lack of security has prevented the agencies from reaching all those in need, progress has been made, he said. For example, food assistance reached 200,000 people in April; that number was expected to more than quadruple this month, he said.
CNN's Saad Abedine, Dan Lothian and Hamdi Alkhshali contributed to this report.
