A military court has since indicted Samaha and Syrian Brig. Gen. Ali Mamlouk of plotting to carry out terrorist attacks. Mamlouk, who was appointed recently by Assad to head Syria's National Security Bureau, was indicted in absentia.
Tensions have been soaring in Lebanon over the conflict next door, and clashes have erupted between Assad supporters 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. Many of Lebanon's Sunnis have backed Syria's mainly Sunni rebels, while Shiites have tended to back 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.
The last 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 neighborhood.
Since then, Lebanese saw a relative calm in violence. After the uprising against Assad began in March 2011, there have been sporadic gunbattles between pro- and anti-Assad factions, particularly in northern Lebanon.
"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."
AP writers Elizabeth A. Kennedy, Ben Hubbard and Barbara Surk contributed to this report from Beirut.