The raid on the desert town of Al-Fuqaha in the south of the Jufra district left three civilians and a policeman dead, Jufra municipal council member Abdellatif Jalala told AFP.
At least five people were killed Monday and 10 others kidnapped in an attack by suspected Islamic State group jihadists on a town in central Libya, local and military sources said.
Three civilians were among the dead, while a soldier was wounded and 10 people "missing, probably kidnapped", said General Ahmed al-Mesmari, spokesman for the Libyan National Army.
The raid targeted the desert town of Al-Fuqaha in Jufra district, which has for over a year been held by forces allied to Libyan strongman Khalifa Haftar, who leads the self-styled LNA.
LNA forces responded to the attack but the IS fighters fled south, killing a five victim and injuring another at a security checkpoint, Mesmari said.
Earlier, municipal council member Abdellatif Jalala told AFP that three civilians and a policeman had been killed in the dawn attack, more than 800 kilometres (490 miles) south of the capital Tripoli.
He said the assailants kidnapped at least eight others before fleeing into the Haruj mountains further south.
Jufra lawmaker Ismail al-Sharif said IS fighters attacked the city with 25 vehicles, beheaded five civilians and torched local government and security offices.
The attackers set fire to police posts and public buildings in Al-Fuqaha, he added.
Both Sharif and Jalala said the raid was likely retaliation for arrests earlier this month of alleged IS members in the area.
The Jufra region has been regularly hit by attacks attributed to jihadists. In August 2017, an attack claimed by IS killed 11 people, including nine LNA fighters.
IS took advantage of the chaos that reigned in Libya after the 2011 NATO-backed ouster of Moamer Kadhafi to establish footholds in several parts of the country.
In June 2015, jihadists seized control of Kadhafi's hometown of Sirte, only ceding it in December of the following year in the face of an offensive by forces loyal to the UN-backed government in Tripoli.
In April this year, the Tripoli-based Government of National Accord launched an operation to track down IS fighters operating in areas of western Libya under its control.
The US military has regularly carried out strikes on jihadists in Libya, particularly south of Sirte.
Many jihadists have since retreated to desert areas in the country's south, where they are attempting to regroup.
A September 10 suicide attack later claimed by IS on Libya's National Oil Company headquarters in the heart of Tripoli left two dead and 10 others wounded.
Four months earlier, IS claimed an attack on Libya's electoral commission headquarters in Tripoli that killed 14 people.