- NEW: State-run media: A "booby-trapped car" explosion kills "many victims"
- Opposition group: Elsewhere, three people are killed across Syria on Saturday
- Ban Ki-moon said he thinks al Qaeda is behind last week's Damascus attack
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(CNN) -- A car explosion shook the city of Deir Ezzor on Saturday, opposition activists and the Syrian regime said, adding to a spate of similar bombings in recent weeks.
The blast took place next to a military and aerial intelligence center, the opposition Syrian Observatory for Human Rights said.
The state-run Syrian Arab News Agency said a "booby-trapped car" claimed "the lives of many victims."
"The terrorist blast caused big damages to the houses, private and public facilities surrounding the site of explosion," the state-run Syrian Arab News Agency said.
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Ajami: Syria is Obama's Rwanda The bombing took place a week after twin suicide bombings in the capital of Damascus killed at least 55 people, wounded a few hundred others and caused widespread damage. The government has blamed "terrorists," while members of the Syrian opposition have blamed the government.
Such incidents have heightened concerns about the possibility of jihadists operating in the country.
U.N. Secretary-General Ban Ki-moon, speaking Thursday at the United Nations, blamed al Qaeda for the Damascus attack.
"Very alarmingly and surprisingly ... there was a huge, serious, massive terrorist attack. I believe that there must be al Qaeda behind it," he said Thursday at the United Nations.
But on Friday, he said, "We are still trying to investigate who are these third forces behind this terrorist attack in Damascus."
Elsewhere across Syria, at least three people were killed Saturday, including two in Idlib and one in Aleppo province, said the opposition Local Coordination Committees of Syria.
The reported deaths came after security forces opened fire on anti-government protesters Friday as they attempted to break up a demonstration, the LCC said.
And a bombing apparently targeted at security forces in Aleppo early Friday, killed one soldier and wounded five others, according to the Syrian Observatory for Human Rights.
Aleppo, the most populous city in Syria, is widely considered a stronghold of President Bashar al-Assad.
Although there have been a number of demonstrations in Aleppo since the Syrian uprising began, the number of people publicly calling for al-Assad's ouster has increased significantly. In an outpouring Thursday, thousands purportedly took to the streets, calling for an end to the regime.
 Map shows area of most recent clashes Map shows area of most recent clashesThe increase in demonstrations in Aleppo comes at a critical time for both sides, which are vying for international support in the conflict that began last year with protests calling for political reforms. It quickly devolved into an armed uprising after a brutal crackdown by al-Assad's forces.
Opposition groups, including members of the rebel army, say al-Assad's government has been trying to thwart their efforts by accusing them falsely of links to terrorists. Al-Assad has dismissed the opposition as foreign-backed terrorists bent on destabilizing the government.
A string of attacks has erupted in recent months in the power centers of Damascus and Aleppo.
The reports of violence have cast severe doubts on the success of the peace plan brokered by U.N.-Arab League joint special envoy Kofi Annan.
Ban and Maj. Gen. Robert Mood, head of the U.N. observer mission in Syria, said 260 observers of 300 planned were deployed in Syria to monitor the progress of the peace plan, which calls for a cease-fire.
"The deployment of monitors has some dampening effect," Ban said. "The number of (instances of) violence has reduced, but not enough. Not all the violence has stopped. So we will continue, as much as we can, to protect the civilian population."
Mood said officials have been "very pleased to see and witness an immediate calming effect brought about by our arrival," but "this has been challenged by asymmetric incidents, sometimes intense, but in some locations."
Ahmad Fawzi, spokesman for Annan, said "both sides" have violated the cease-fire.
At least 27 people died in Syria on Friday, the LCC said.
In recent days, violence has spilled into Lebanon and Turkey, where thousands of Syrians have fled. At least one person was killed and an undetermined number were wounded Thursday in renewed clashes in the northern Lebanese city of Tripoli between factions supporting and opposing the uprising in Syria, Lebanon's National News Agency reported.
Ban said 9,000 to 10,000 people have been killed during the crisis. Opposition activists have reported a death toll of more than 11,000.
CNN cannot independently verify reports of deaths and violence because the Syrian government has severely restricted access by international media.
CNN's Kamal Ghattas, Amir Ahmed and Richard Roth contributed to this report.
