A car bomb has rocked a stronghold of the Shia militant group Hezbollah south of the Lebanese capital, Beirut, setting several cars alight and wounding 37 people in a major security breach of a tightly guarded area, officials said.

The powerful blast in a bustling commercial and residential neighbourhood on Tuesday, the worst explosion to hit the area in years, came as many Lebanese Shias began observing Ramadan, and is likely to be direct fallout from the civil war raging in neighbouring Syria.

A group of about 100 outraged Hezbollah supporters marched in the area after the blast, carrying pictures of the Hezbollah chief Hassan Nasrallah and shouting in support of their leader.

Hezbollah operatives fired into the air to disperse people who attacked the interior minister, Marwan Charbel, with stones as he inspected the scene of the blast, trapping him for 45 minutes in a building before he was escorted through a backdoor.

Charbel is seen by some Shias as sympathetic to the hardline Sunni cleric Ahmad al-Assir, who agitated against Hezbollah for months and is now on the run.

With skirmishes between Shias and Sunnis on the rise around the country, Lebanon is increasingly buffeted by powerful forces that are dividing the Arab world along sectarian lines. Some Syrian rebel groups, which are predominantly Sunni, have threatened to strike in Lebanon after Hezbollah joined the troops of the Syrian president, Bashar al-Assad, in their battle against opposition fighters.

"This is a message, but we will not bow," Ziad Waked, a municipal official, told Hezbollah's al-Manar television.

Officials said the blast was in a parking area near a supermarket and a petrol station in the Beir el-Abed district.

"The explosion was so strong I thought it was an Israeli air raid," said one witness, Mohammad al-Zein. "My wife was sleeping in bed and all the glass fell on her, injuring her in the mouth, arms and legs."

Another resident said he had been fasting on the first day of Ramadan and was on his way to shop for the evening meal. "I was riding my motorcycle on my way to a sweets shop and then there was this massive explosion that knocked me off and I fell on the ground," he said.

The Red Cross's head of operations, George Kattaneh, said 37 people had been lightly wounded, many from breaking glass.

The area is a few hundred metres from what is known as Hezbollah's "security square", where many of the party's officials live and have offices. Nasrallah received dignitaries there before the 2006 war. The area was bombed out by Israel in that conflict and Nasrallah has gone underground since then, only rarely appearing in public and never for more than a few minutes for fear of Israeli assassination.

The explosion was one of the biggest in the area since the end of Lebanon's 15-year civil war in 1990. Television footage from the scene revived memories of the war, when car bombs set by sectarian groups were common. There have been numerous car bombs targeting politicians and journalists since then, but random car bombs have been rare.

Hezbollah operatives in civilian clothes, some of them carrying Kalashnikov rifles, cordoned off the site of the explosion with yellow ribbons. They and Lebanese security officials barred journalists from approaching the site itself.

Ambulances and fire engines, their sirens wailing, raced to the area and witnesses said casualties were rushed to the nearby Bahman and Rasoul al-Atham hospitals. Immediately after the blast, people could be seen running in the street away from the site of the explosion which set several cars on fire.

The power of the explosion shattered windows and damaged several buildings in the area. A security official said the bomb had been placed in a car and weighed 35kg.