A Libyan criminal court has sentenced 45 militiamen to death by firing squad for killing demonstrators in Tripoli in 2011, the justice ministry says.

They are accused of opening fire on dozens as rebel forces closed in on the capital during the uprising against former leader Colonel Muammar Gaddafi.

It is thought to be the highest number of death sentences handed out since the overthrow of the regime, an agency reports.

Libya has struggled to restore peace since the uprising seven years ago.

Aside from the 45 sentenced to death, 54 more were given five-year jail terms and another 22 were acquitted of charges relating to demonstrator deaths.

It was not known when the accused were arrested, charged or prosecuted.

The case, referred to by the Libyan Justice Ministry as Abu Salim No 2015-1477, is known locally as the Triq al-Sareeh case.

It refers to an incident when residents of the Abu Salim district of Tripoli took to the streets to prematurely celebrate the capital nearing liberation, only to be allegedly shot dead near a highway by pro-Gaddafi residents living nearby.

The death sentences announced on Wednesday are the first known to be handed down by a Tripoli court since 2015.

Back then, dozens of high-profile Gaddafi-era regime officials, including his son Saif al-Islam, were sentenced to death by firing squad.

Those verdicts have not been carried out and historically most death sentence prisoners in Libya have ended up sending life in prison instead.

The years since the overthrowing and killing of Colonel Gaddafi have been marred by violence and instability in Libya, with no authority in full control.

The country has splintered and since 2014 has been divided into competing political and military factions based in Tripoli and the east.

Earlier this year some rival factions agreed to hold parliamentary and presidential elections later this year.

But international observers, including human rights groups and politicians abroad, have cast doubt on whether the ballot should and will go ahead.