Armed men have abducted at least six peaceful protesters in Libya's capital and used live fire to disperse a demonstration wounding others, Amnesty International said on Wednesday.

The protest was one of several that took place Sunday against poor public services and living conditions, with other rallies erupting in the country's third-largest city Misrata and Al-Zawyia west of the capital Tripoli.

"At least six peaceful protesters were abducted and several others were wounded after armed men fired live ammunition including from heavy machine-guns to disperse a demonstration in Tripoli," Amnesty said in a statement.

The London-based rights group said Sunday's attack took place in a district controlled by a militia aligned to Tripoli's UN-recognised Government of National Accord (GNA).

It was carried out by "unidentified armed men wearing military-style camouflage clothes (who) opened fire," Amnesty said, citing video evidence, photos and witnesses.

Witnesses said that no warning was given before the live rounds were fired and gave "stong indications" that the militia was responsible, the watchdog said.

"Videos also show assailants using a heavy machine-gun mounted on a pick-up truck to fire live rounds into the air to disperse the protesters," Amnesty added.

On Wednesday, GNA leader Fayez al-Sarraj chaired a security meeting that discussed "the clashes" in Tripoli and what triggered them.

A statement by the GNA on Facebook added that the meeting underscored the need to "implement measures to ensure the safety of citizens".

It also called for a probe into "violations" committed against the protesters, including anyone who sustained injuries, and ordered the release of those not involved in acts of "vandalism", it added.