Four civilians were killed on Tuesday when a projectile exploded in a vegetable market in an eastern suburb of Libya's capital, a rescue workers' spokesman said.

"Four civilians were killed and six wounded by an explosive device that targeted the Tajoura vegetable market," Oussama Ali told AFP.

Forces loyal to the United Nations-recognised Government of National Accord, based in Tripoli, accused rival forces answering to eastern warlord Khalifa Haftar of hitting a "civilian area".

Haftar's forces, who have since April carried out an offensive against the capital, made no immediate comment on the attack.

An AFP photographer at the scene confirmed the projectile had exploded near a vegetable market, located in an area controlled by forces backing the GNA.

Shell fragments fell on cars and buildings in an area stretching several dozen metres, the photographer said.

According to UN figures published last week, the fighting around Tripoli since April 4 has killed at least 284 civilians and wounded 363.

More than 140,000 Libyans have been forced to flee their homes over the same period.

The country has been mired in chaos since Muammar Gaddafi was deposed and killed in a 2011 NATO-backed uprising.