Four people have been killed in a suicide attack in the eastern Libyan city of Benghazi, after a suicide bomber blew up his car at a checkpoint manned by armed youths, fighting alongside government forces against Islamist groups, witnesses said.

Benghazi Medical Centre said they had received three bodies and the remains of the suicide bomber, and are treating those who were injured in the attack on Friday.

The attack targeted residents of the central Benghazi area of Boudhima, who had apparently set-up a roadblock at the entrance to their neighbourhood.

Violence between Islamists and pro-government forces battling for control of the Libyan city already claimed at least 16 lives on Friday.

The Benghazi Medical Centre said those killed were mostly soldiers and civilians fighting alongside the army in the central district of al-Majouri.

Street battles

At least 52 people have been killed since forces of retired General Khalifa Haftar, backed by army units, on Wednesday launched what he called an operation to "liberate" Benghazi from Islamist groups, according to hospital figures.

The offensive came after al-Qaeda-linked Ansar al-Sharia and other armed groups overran some army camps and were closing in on the airport.

Civilians have been caught up in the fighting and the Red Crescent charity has called for a ceasefire to allow civilians to escape the fighting.

"They shelled our house in the middle of the night. My son was injured but when we got him to hosiptal the doctors said they couldn't do anything for him and he died," Issa Abdel Salam, a man displaced by fighting, told Al Jazeera.

Al-Majouri is home to the leader of Ansar al-Sharia, Mohamed al-Zehawi, and many of his men.

Residents said the two sides used weapons of all calibres in street fighting in a densely-populated district.

There was no word on casualties on the side of the Islamists, who rarely announce their losses.

Three years after the ousting of Muammar Gaddafi, turmoil remains in the port city, home to several oil firms.

The plight of Benghazi underlines the central government's inability to control rival armed factions that once fought Gaddafi and now battle over post-war spoils.

Source: AFP