(CNN) -- The embattled Syrian regime, reacting after a suicide bombing in the capital and continued violence in several anti-government bastions, vowed Friday to confront its foes with stern resolve as more than 60 deaths were counted across the nation.
"We will strike with an iron fist anyone who tampers with the security of the nation and citizens and we call our citizens to alert any suspicious situation," the Interior Ministry said, according to state media.
The Damascus suicide bombing, the second such strike in the capital in two weeks, took place in the al-Midan quarter of the city. Casualties included mostly civilians and some law enforcement personnel, the Syrian Arab News Agency said. At least 26 people died and at least 63 people were injured, SANA said.
Car and suicide bombings have long been common in the wars in Iraq and Afghanistan. But this development in Syria, similar to the strikes carried out December 23 on government security targets, deepened the fears of full-blown warfare in the nation.
Outside the capital, 35 people were killed as security forces confronted protesters in the Damascus suburbs and the provinces of Homs, Hama, Idlib and Daraa, activists said.
The apparent suicide attack and the clashes across Syria occurred as Arab League monitors are in the country to determine whether the Syrian government is abiding by an agreement to end its 10-month crackdown against protesters.
The Arab League said Friday it will increase the number of monitors in Syria over the next few days from 100 to 150 people. The monitors' presence since last week has failed to decrease the violence.
A statement issued on behalf of Ban Ki-moon said the secretary-general "condemns the terrorist bombing" and "reiterates that all violence is unacceptable and must stop."
In the Damascus attack, SANA said a suicide bomber blew himself up just before 11 a.m. in a densely populated area near Hassan al-Hakeem Basic Education School. The news agency posted photos of the aftermath showing victims, vehicles with shattered windows and pools of blood.
The strike comes a couple of days after the Free Syrian Army -- the force of military defectors fighting President Bashar al-Assad's regime -- vowed to kick off "huge operations" against government targets.
SANA quoted an official saying that the initial death toll in the explosion was 11 and that authorities were working to identify 15 others whose remains were found.
No one has claimed responsibility, but one high-ranking Free Syrian Army officer denied blame and said regime forces conducted the blast.
"The explosion in Damascus today is the work of the Syrian intelligence because they had information that a massive protest was planned in the al-Midan district," said Lt. Col. Mohamed Hamado.
"The FSA does not conduct operations of that kind that may kill civilians, and we are in direct contact with Col. Riad al-Asaad, head of FSA, before executing any attack. We have confirmed information that the intelligence is funding and has formed units that perform terrorist operations under names of Islamic extremist groups and issue statements on the Internet, so that the government proves to the West that Islamic extremists are a threat and may take over if the regime is toppled."
The opposition Syrian National Council blamed the regime for sowing "chaos" and diverting attention from its own "crimes of murder and torture." It said the regime "bears the full responsibility for both the explosion and its perpetrators."
"The SNC had previously warned that the regime was planning to carry out bombing attacks in several areas in Syria. Today's bombings, in the area that has experienced the largest of the anti-regime demonstrations, clearly bear the regime's fingerprints," the group said in a statement.
Abdel Karim Rihawi, head of the Cairo-based activist group the Syrian Human Rights League, agreed about who the perpetrator is.
"The regime orchestrated the explosion in Damascus, as a fake message to the monitors that there are so-called terrorists conducting operations," Rihawi said.
One activist told CNN that the government was looking for an excuse to block off central Damascus as protesters planned to converge on the area. Abu Yassir, a pseudonym for a 22-year-old from the neighborhood, told CNN he was at home when he heard the blast erupt a couple of streets away. He didn't immediately leave the house to see what had happened because security forces were blocking the area.
Five demonstrations began at various mosques in al-Midan, with at least one of them near the blast.
"Three of them are very big," Yassir said, with thousands of people. He said security forces arrested at least 50 people, including a 10-year-old boy who was beaten at the time of his arrest.
Al-Midan, he said, is one of the few central Damascus neighborhoods where demonstrations erupted. He said activists have been doubting the scale and the death toll described by the government.
"Bashar al-Assad can't stop us," Yassir said. "Even if he kills us every day, shoots us, arrests too many of us, he can't stop us."
Another witness from al-Midan, an activist who goes by the pseudonym Mar, described a chaotic scene after hearing the blast and said people demonstrated en masse throughout the neighborhood. He said security forces made arrests and shot and wounded people. Mar said pro-government thugs armed with knives and small swords chased protesters.
Every Friday for months, anti-government activists have staged mass demonstrations across Syria, each week having a different theme. This week's theme had the slogan, "In fighting tyranny, belief in God will grant you victory."
The Local Coordination Committees of Syria, a network of opposition activists that organizes and documents protests, reported a heavy presence of ambulances and security forces in Damascus.
The LCC reported massive outpourings of protesters in Aleppo and a huge deployment of security forces in other parts of the country. At least 35 people were killed in those demonstrations, the LCC said: 14 in the Damascus suburbs, nine in Hama province, eight in Homs province, three in Idlib province, and one in Daraa province.
The LCC said security forces firing at protesters shot a child in the chest in the city of Deir Ezzor and, in the Damascus suburbs, killed a teenager whose grandfather is a sheikh.
The activist group also reported security forces killed three soldiers in the Homs province town of Rastan "because they refused to fire at peaceful protesters."
According to an activist from Rastan, the three soldiers were at a checkpoint when they attempted to run away and join the Free Syrian Army in the area. As soon as they started running away, they were shot and killed, and their bodies were taken by the Syrian army, the activist said.
An Arab League official who asked not to be named said Friday that residents in Arbeen outside of Damascus encircled monitors Thursday. Security forces fired at crowds, leaving the monitors in a "dangerous" situation, the official said.
Hamado, who is in charge of Free Syrian Army operations in the coastal city of Latakia, said the regime is detaining protesters in cargo containers, loading them on ships and transferring them to security headquarters. He said the regime has been detaining women and blackmailing men by saying if they do not turn themselves in the women will be raped. He charged that the crackdown in Latakia is being led by Hafez Munzer al-Assad, the son of the president's first cousin.
"Everything is expensive now," Yassir of al-Midan said about sanctions-plagued Syria. But human life is cheap, he said.
"The humans in here are just like bullets, two Syrian pounds."
Estimates of the death toll have ranged from more than 5,000 to more than 6,000 during the months-long protests and crackdown. Activists blame the killings on the government, but al-Assad's regime says it is putting down armed terrorists, whom it blames for the bloodshed.
CNN cannot independently confirm events inside Syria because the government has restricted activities by international journalists.
CNN's Nada Husseini, Tracy Doueiry and Pierre Meilhan contributed to this report.