* Captured militant may help uncover radical jihadi cells
* Organised car bomb attacks on Shi'ite targets in Lebanon (Adds weapons depots discovered)
By Mariam Karouny
BEIRUT, Feb 12 (Reuters) - Lebanon's army on Wednesday arrested a senior al Qaeda-linked militant described by officials as a "mastermind of car bombs" hitting Shi'ite areas in recent months, triggering a major security sweep in the country.
Security sources said the arrest of Naim Abbas, who confessed to his organisational role, helped uncover two booby-trapped cars, two weapons depots and led to the arrest of several jihadi-linked people.
They added his arrest would also help uncover more radical jihadi cells that have been targeting army posts and Shi'ite areas under the control of the Lebanese Shi'ite Hezbollah group.
The surge in violence in Lebanon is linked to the three-year conflict in neighbouring Syria, with sectarian tensions between Sunni and Shi'ite Muslims rising on both sides of the border.
The security sources said Abbas played a role in four recent car bomb attacks in southern Beirut and two more in the mostly Shi'ite town of Hermel in eastern Lebanon, all Hezbollah strongholds. Scores of civilians were killed in the attacks.
Abbas's capture is the second major one after another al Qaeda-linked leader, Majid al-Majid, was seized in December. He died in custody due to kidney failure.
"He (Abbas) drove the suicide bombers to the southern suburbs. He is the mastermind of car bombs, he is as important as Majid al-Majid," another source said.
Hours after Abbas's arrest, security forces found a car loaded with 100 kg of explosives in the Corniche al-Mazraa district of central Beirut and another one with explosives near the town of Arsal, on the frontier with Syria.
A Lebanese army statement said three women were inside the second car, which had come from Yabroud in Syria where the Syrian army is preparing an offensive to flush out rebels. The women's task was to deliver the car to potential suicide bombers, the statement said.
"It was he (Abbas) who confessed and gave the location of these two cars. So far two cars have been discovered but many more will follow," a security source told Reuters.
The army later raided two villages in southern Beirut, Saadeyat and Debeyi, where it confiscated dozens of 107mm rockets, security sources added.
The army also said it had had Abbas under surveillance for some time after receiving information about his involvement in recent bombings.
Abbas, a Palestinian, was snatched from his house in a Beirut suburb in a special operation led by the Lebanese army in the early hours of Wednesday.
Lebanon, which is still recovering from its own 1975-1990 civil war, has been struggling to stem the spillover of violence from Syria.
Hezbollah has sent fighters and advisers to help its ally President Bashar al-Assad, a member of the Shi'ite-derived Alawite minority, against mainly Sunni rebels who have become dominated by Islamist fighters.
Groups in Lebanon linked to Al-Qaeda have accused Hezbollah of interfering in Syria and said they will launch attacks against the group.
(Additional reporting by Laila Bassam; Editing by Tom Heneghan)