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The aftermath of the car bomb explosion in the Hezbollah stronghold of Haret Hreik in southern Beirut.
A powerful car bomb exploded near a Hezbollah security zone in southern Beirut on Thursday, killing at least five people and wounding dozens more in the fifth such attack on the militant group's heartland since July.

The blast came a week after another bomb killed a senior opposition figure and seven other civilians in the downtown area of the Lebanese capital. The explosions have marked a deterioration in security across the country widely believed to stem from the war in neighbouring Syria, which has kindled long-standing regional rivalries.

Thursday's attack hit the Haret Hreik district of the suburb of Dahiyeh, which has long been an operations hub for Hezbollah. The organisation said none of its people or sites had been affected.

The increasing frequency of the attacks has, however, instilled widespread fear among the group's supporters and those who live in areas protected by Hezbollah and other Shia militias. Four of the attacks have been in civilian neighbourhoods.

A blast in July that wounded at least 50 people was followed on 15 August by an attack that killed at least 20. In November, twin suicide bombers targeted the Iranian embassy, killing another 23 people, including an Iranian diplomat.

Last month, a senior Hezbollah figure, Hassan Laqqis, who directed logistics for the organisation, was assassinated by gunmen using silenced weapons outside his Beirut apartment.

In Tripoli, at the other end of the country, two explosions in August outside Sunni mosques killed more than 40 people.

Community leaders and many of those killed had been vocal supporters of the largely Sunni opposition in Syria. Hezbollah, meanwhile, robustly backs the Syrian regime, which draws much of its support base from Shia Islamic interests, including Iran, the Alawite sect and a large Iraqi Shia militia.

As the Syrian war has worsened, Lebanese political leaders from these two main blocs have insisted they are trying to quarantine the feeble state from steeply rising sectarian tensions over the border.

The western-leaning 14 March faction has sent weapons and funds to the Syrian opposition, while in May, Hezbollah's leader, Hassan Nasrallah, revealed the depth of his organisation's support for the Assad regime, on which it has relied for support since its inception more than 30 years ago. Mohammed Shatah, senior 14 March official, was killed in last week's car bombing.

Both sides suggest their involvement in Syria is a counterweight to the other and have repeatedly said that importing the war to Lebanon serves neither of them. The rising number of interests in the war and the vehemence of the protagonists is, however, making attempts to control Lebanon evermore difficult.

Also on Thursday, the Saudi ambassador to Lebanon confirmed that Saudi national Majed al-Majed, whom local authorities believe is the leader of an al-Qaida affilliated group, the Abdullah al-Azzam Brigades, had been captured in Beirut on Monday. He is being questioned in relation to the Iranian embassy bombing, which the group claimed responsibility for shortly after the attack.

Nasrallah had previously accused Saudi Arabia of being responsible for the bombing, a claim Riyadh denied.

The Beirut blast comes a day after it was reported that Lebanese authorities had captured a militant leader suspected of leading a group that claimed responsibility for the bombing of the Iranian embassy in Beirut, in November.

Majid bin Muhammad al-Majid is believed to be the leader of the al-Qaida-inspired Abdullah Azzam Brigades, which claimed responsibility for the 19 November attack that killed 25 people, including an Iranian diplomat.

He is believed to have been arrested on Monday by an intelligence unit of the Lebanese military.