Police chief Ashraf Rifi identified the dead officer as Captain Wisam Eid, whose vehicle was caught in the blast as he was on his way to work. A bodyguard was also killed.
Eid worked for an intelligence unit which is widely viewed as close to anti-Syrian ruling coalition leader Saad al-Hariri.
"Eid had a role in all the files linked to terrorist bombings," the police chief told reporters at the scene.
Eid took up his post after his predecessor Samir Shehadeh was wounded by a roadside bomb south of Beirut in 2006.
The police intelligence unit has been closely involved in the U.N.-led investigation into the 2005 assassination of Hariri's father, former Lebanese Prime Minister Rafik al-Hariri, and in a crackdown on al Qaeda-inspired militants.
Firemen sprayed water over blazing cars and debris scattered over a road in the suburb of Hazmiyeh. A charred corpse was visible in one car. Body parts were strewn on the road.
Dozens of vehicles were damaged in the explosion, which ripped a large crater in the road.
The explosion occurred 10 days after a car bomb damaged a U.S. diplomatic car in the Lebanese capital, killing three people and wounding 16. No Americans were among the dead.
Last month a car bomb killed the army's chief of operations, Brigadier-General Francois Haj, in east Beirut.
SERIES OF BOMBINGS
Interior Minister Hassan al-Sabaa told LBC television that Eid had been a key member of the police intelligence unit and had been attacked before.
"This will not affect our morale and it will not make us change course in piloting the country to safety," he said.
This was the second attempt to kill him. Two years ago a hand grenade had been thrown at his home in Beirut.
The majority coalition accuses Syria of being behind Hariri's assassination and many of the 30 or more bombings that have hit Lebanon in the last three years. Many have been against anti-Syrian politicians and journalists.
Damascus denies any involvement.
Bombers have also attacked U.N. peacekeepers in the south, while a revolt by al Qaeda-inspired Islamist militants in the north last year further undermined Lebanon's stability.
Apart from its security problems, Lebanon is in the thick of a long-running political conflict pitting the Western-backed ruling coalition against the Hezbollah-led opposition.
The dispute has paralysed government for more than a year and blocked election of a new president, leaving Lebanon with no head of state for the first time since its 1975-90 civil war.
Rival factions have agreed that army commander Michel Suleiman should be the next president, but remain at odds over how to share power in a future national unity government.
Mediation by Arab League Secretary-General Amr Moussa has failed to bridge the gulf. He is due to report on his efforts to Arab foreign ministers meeting in Cairo on Sunday.
Map locates Beirut, Lebanon, where an explosion killed at least 10 people including Senior intelligence officer Wisam Eid
Cars burn at the site of explosion in Beirut, Lebanon Friday, Jan. 25, 2008.
A man reacts to the death of his son where an explosion killed at least 10 people including Senior intelligence officer Wisam Eid
People gather at the site of explosion in Beirut, Lebanon Friday, Jan. 25, 2008
Sources: Reuters , Ya Libnan
Tags: Hariri, Lebanese, Lebanon, Syria, Wissam Eid
