Residents watched as the body was hung in the village square
Lebanese officials are investigating the lynching by angry villagers of an Egyptian man accused of killing a local couple and their two grandchildren.
The suspect was with police re-enacting the crime when he was seized by a mob in a village south of Beirut, according to Lebanese media reports.
The mob stabbed him to death and then hanged him with a butcher's hook from a pole in the village square.
Officials condemned the action by villagers as "barbaric".
Interior Minister Ziad Baroud ordered an investigation and said such vigilante action was "extremely dangerous".
Mohammed Muslem, a 38-year-old Egyptian reportedly working as a butcher in Ketermaya village, had been arrested on suspicion of killing an elderly couple and their granddaughters aged seven and nine.
He is said to have confessed and was leading police officers through the events of the day when dozens of villagers dragged him away from police custody and began beating him with sticks and knives.
Some witnesses said police rescued him and took him to a nearby hospital, only for the crowd to break in to the intensive care unit, drag him out and continue to beat him.
After killing Mohammed Muslem, the mob is reported to have stripped him down to his underpants, driven his body through the streets on a car bonnet, and then hung him from a pole in the centre of the village with onlookers crying "Allahu Akbar" or God is Great.
The army was finally able to intervene after 30 minutes and took his body away.
"Whatever the feeling of the villagers, nothing can justify this type of reaction," Justice Minister Ibrahim Najjar said.
"We have the names of at least 10 people who took part in this horrible crime and the courts must now do their work. No state of law can condone what happened."
But villagers were unrepentant. "This man came to this village and he did a big crime..." one villager was quoted by Reuters news agency as saying. "And thank God the village took revenge with our own hands."