A car bomb ripped through Beirut on Friday, killing a top security official and seven others, shearing the balconies off apartment buildings and sending bloodied residents staggering into the streets in the most serious blast the Lebanese capital has seen in four years.

Dozens of people were wounded in the attack, which the state-run news agency said targeted the convoy of Brig.-Gen. Wissam al-Hassan, a top security official in Lebanon.

Many Lebanese quickly raised the possibility the violence was connected to the civil war in neighbouring Syria, which has sent destabilizing ripples through Lebanon for the past 19 months. Al-Hassan was in charge of an investigation that exposed a bomb plot over the summer, leading to the arrest of a pro-Syrian Lebanese politician and charges against a top Syrian regime figure.

"Whenever there is a problem in Syria they want to bring it to us," said Karin Sabaha Gemayel, a secretary at a law firm a block from the bombing site, where the street was transformed into a swath of rubble, twisted metal and charred vehicles.

"But you always hope it will not happen to us. Not again," she said.

A Lebanese first responder carries an injured boy at the scene of an explosion in Beirut that killed at least eight people and injured dozens more. (Hussein Malla/Associated Press)

The blast ripped through a narrow street at mid-afternoon in Beirut's mainly Christian Achrafieh neighbourhood, an area packed with cafés and shops. Doors and windows were shattered for blocks, and several blackened cars appeared to have been catapulted through the air.

Bloodied residents fled their homes while others tried to help the seriously wounded. One little girl, apparently unconscious and bleeding from her head, was carried to an ambulance in the arms of rescue workers, her white sneakers stained with blood.

"I was standing nearby in Sassine Square and I heard a big explosion and I ran straight to it," resident Elie Khalil said. He said he saw at least 15 bloodied people in a nearby parking lot before medics arrived and took them to a hospital.

Close to 80 people wounded

Lebanese security officials said eight people were killed and 60 wounded, 20 of them critically. The officials spoke on condition of anonymity because they weren't authorized to talk to the press. The state-run National News Agency put the number of wounded at 78.

Health Minister Ali Hussein Khalil called on all hospitals to accept the wounded from this "terrorist bombing."

Canadian Foreign Affairs Minister John Baird said he was shocked and deeply troubled by the attack.

“Canada strongly condemns this cowardly act of terrorism and supports efforts to bring the perpetrators to justice," he said. “Canada is a strong supporter of the Special Tribunal for Lebanon and its efforts to render justice for acts of terrorism in Lebanon, including the [former prime minister Rafik] Hariri assassination and related cases.”

The UN Security Council also condemned the attack.

"The members of the Security Council reiterated their unequivocal condemnation of any attempt to destabilize Lebanon through political assassinations and demanded an immediate end to the use of intimidation and violence against political figures," Guatemala UN ambassador Gert Rosenthal, the current Security Council president, said in a statement.

"[The council] appealed to all Lebanese people to preserve national unity in face of such attempts to undermine the country's stability and called upon all Lebanese parties to continue engaging in the National Dialogue reconvened under the authority of President Sleiman to this effect."

Hit by wave of bombings

Friday's blast was a reminder of Lebanon's grim history, when the 1975-1990 civil war made the country notorious for kidnappings, car bombs and political assassinations. Since the war's end, Lebanon has been a proxy battleground for regional conflict, and the Mediterranean seaside capital has been prey to devastating violence shattering periods of calm.

Tensions have been soaring in Lebanon over the conflict next door, and clashes have erupted between supporters of Syrian President Bashar al-Assad and backers of the rebellion against his regime.

Syria and Lebanon share a complex web of political and sectarian ties and rivalries, often causing events on one side of the border to echo on the other. Lebanon's Sunnis have tended to back Syria's mainly Sunni rebels, while Lebanon's powerful Shiite Hezbollah movement is a key ally of Assad.

Lebanon was hit by a wave of bombings and other attacks that began in 2005 with a massive suicide blast that killed former prime minister Rafik Hariri and more than 20 other people in downtown Beirut. In the following years, a string of anti-Syrian figures were assassinated, several in car bombings. Many Lebanese blamed Damascus for the killings, though Syria denied responsibility.

Al-Hassan, the official targeted Friday, had headed an investigation that led to the Aug. 9 arrest of former information minister Michel Samaha, one of Syria's most loyal allies in Lebanon who has long acted as an unofficial media adviser to Assad.

Explosives moved from Syria to Lebanon

According to a senior Lebanese police official, Samaha confessed to having transported explosives in his car from Syria to Lebanon with the purpose of killing Lebanese personalities at the behest of Syria.

A military court has since indicted Samaha and Syrian Brig.-Gen. Ali Mamlouk of plotting to carry out terrorist attacks inside Lebanon. Mamlouk, who was appointed recently by Assad to head Syria's National Security Bureau, was indicted in absentia.

The last massive serious bombing was in 2008, when a car bomb killed a senior Lebanese anti-terror police official who was investigating dozens of other bombings. Four others were killed and 38 wounded in the blast in the Christian Hazmieh neighbourhood.

Since then, Lebanese saw a relative calm in violence. After the uprising against Assad began in March 2011, there have been sporadic gun battles between pro- and anti-Assad factions, particularly in northern Lebanon. The divisions also tend to fall along sectarian lines, a dangerous element in a country that was torn apart by the 1975-1990 civil war.

"I'm very worried about the country after this explosion," Beirut resident Charbel Khadra said Friday. "I'm worried the explosions will return — and this is just the first one."

Soon after the blast erupted, crowds began blocking roads, burning tires and shooting in the air in Sunni areas of Beirut and northern Lebanon. In the eastern Bekaa Valley, angry protesters closed the border crossing that links Lebanon with Syria.

In the northern Lebanese city of Tripoli, pro- and anti-Syrian groups fought with rocket-propelled grenades and automatic rifles.

One person was killed, according to security officials. Elsewhere, clashes pitted gunmen in a Sunni neighbourhood against those in an Alawite neighbourhood of the city. Assad belongs to the tiny Alawite sect, an offshoot of Shiite Islam.

Even as the rubble smouldered in Beirut, Lebanon's fractious political leaders began taking sides. Syria ally Hezbollah condemned the attack and expressed a "state of great shock over this terrible terrorist crime."

Blame placed on Assad

But the anti-Syrian blocs placed the blame squarely on Assad.

Former prime minister Saad Hariri, a Sunni politician whose powerful father was assassinated in 2005 in a massive truck bombing along the Beirut waterfront, said the Lebanese people must not remain silent about this "heinous crime."

Asked who he blamed, Hariri said: "Bashar Hafez Assad."

Speaking to the Al Arabiya TV station, Walid Jumblatt, leader of the Druse sect, also accused Assad of being behind the killing.

"He is telling us that even though he turned Syria into rubble, 'I am ready to kill in any place"' Jumblatt said.

For much of the past 30 years Lebanese have lived under Syrian military and political domination.

That grip began to slip in 2005, when former prime minister Rafik Hariri was assassinated. Syria was widely accused of involvement — something it has always denied — and Damascus was forced to withdraw its troops.

But the killings of anti-Syrian figures continued for several years, and opponents of Assad say he has maintained his influence through proxies in the government.

"The fate of Syria and Lebanon were, are and will always be inextricably linked, for better or worse," said Bilal Saab, a Syria expert at the Monterey Institute of International Studies in California.