Lebanon’s interior minister says the death toll from the powerful car bomb that struck a south Beirut suburb has risen to 22.

Marwan Charbel also says that officials are conducting DNA tests on Friday on body parts discovered near the vehicle that blew up to try to determine whether the explosion was the work of a suicide bomber.

Thursday’s blast struck a bustling street in the Rweiss district in a southern suburb of Beirut that is a stronghold of the Lebanese Shiite militant group Hezbollah.

The bombing was the second in just more than a month to hit a Hezbollah stronghold south of Beirut.

Many people in Lebanon see the attacks as retaliation for Hezbollah’s armed support for President Bashar Assad in neighboring Syria’s civil war.

Earlier, a powerful car bomb tore through a bustling south Beirut neighbourhood that is a stronghold of Hezbollah on Thursday and trapping dozens of others in an inferno of burning cars and buildings in the bloodiest attack yet on Lebanese civilians linked to Syria’s civil war.

The blast is the second in just over a month to hit one of the Shia militant group’s bastions of support, and the deadliest in decades. It raises the spectre of a sharply divided Lebanon being pulled further into the conflict next door, which is being fought on increasingly sectarian lines pitting Sunnis against Shias.

Syria-based Sunni rebels and militant Islamist groups fighting to topple Syria’s President Bashar Assad have threatened to target Hezbollah strongholds in Lebanon in retaliation for intervening on behalf of his regime in the conflict.

Thursday’s explosion ripped through a crowded, overwhelmingly Shia area tightly controlled by Hezbollah, turning streets lined with vegetable markets, bakeries and shops into scenes of destruction.

Dozens of ambulances rushed to the site of the explosion and fire-fighters used cranes and ladders to try to evacuate terrified residents from burning buildings. Some fled to the rooftops of buildings and civil defence workers were still struggling to bring them down to safety several hours after the explosion.

The blast appeared to be an attempt to sow fear among the group’s civilian supporters and did not target any known Hezbollah facility or figure.

The army, in a statement, said the explosion was caused by a car bomb. It called on residents to cooperate with security forces trying to evacuate people trapped in their homes.

Syria’s conflict has spilled across the border into its neighbour on multiple occasions in the past two years. Fire from Syria has hit border villages, while clashes between Lebanese factions backing different sides have left scores dead.

But direct attacks against civilian targets were rare until Hezbollah stepped up its role in Syria. Since then, its support bases in southern Beirut have been targeted. Since May, rockets have been fired at suburbs controlled by the group on two occasions, wounding four people. On July 9, a car bomb exploded in the nearby Beir al-Abed district, wounding more than 50 people.

It came despite rigorous security measure taken in the past few weeks by Hezbollah around its strongholds, setting up checkpoints, searching cars and sometimes using sniffer dogs to search for bombs. It also came a day before Hezbollah’s leader was scheduled to give a major speech marking the end of the month-long 2006 war with Israel.

The explosion occurred on a commercial and residential main street in the Rweiss district, about 100 meters (yards) away from the Sayyed al-Shuhada complex where Hezbollah usually holds rallies.

Panicked Hezbollah fighters fired in the air to clear the area and roughed up photographers, smashing and confiscating some of their cameras following the explosion.

Sunni-Shia tensions have risen sharply in Lebanon, particularly since Hezbollah raised its profile by openly fighting alongside Assad’s forces. Lebanese Sunnis support the rebels fighting to topple Assad, a member of a Shiite offshoot sect.

The group’s fighters played a key role in a recent regime victory in the town of Qusair near the Lebanese border, and Syrian activists say they are now aiding a regime offensive in the besieged city of Homs.

A previously unheard-of group calling itself Aisha the Mother of Believers Brigades claimed responsibility for the attack in a video posted on YouTube, saying it is the second “message” they sent since last month’s blast in the area. The authenticity of the claim could not be independently verified.

“Our second message was strong and astounding,” said a masked man who read the statement, flanked by two other armed and masked men. He called on civilians to stay away from Hezbollah strongholds in the future, saying the militant group is “an agent for Iran and Israel.”

Politicians within Lebanon’s Western-backed coalition have slammed the group for its involvement in Syria and called for its disarmament.

The U.N. Security Council strongly condemned the terrorist attack, calling it a “heinous act.” Council members stressed that terrorism “constitutes one of the most serious threats to international peace and security, and that any acts of terrorism are criminal and unjustifiable.”

U.S. ambassador to Lebanon Maura Connelly also strongly condemned the bombing. In comments posted on the embassy’s Facebook page, Connelly called for all parties to exercise calm and restraint.

The British Foreign Office official in charge of Middle East policy, Alistair Burt, also condemned the attack.

“Terrorism and extremism have no place in Lebanon. I call for the Lebanese state to investigate this urgently and bring the perpetrators to justice,” he said in a statement.

Outgoing Lebanese Prime Minister Najib Mikati declared Friday a day of mourning for the victims of the attack.

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