At least 16 killed in two days of Libya clashes
Fighting between government forces and tribal fighters in the southern Libyan town of Kufra has continued for a second day, officials said.
At least 16 people have died since the clashes began on Saturday, with women and children among the dead.
Libya's government has been struggling to maintain security since the ousting of Muammar Gaddafi last year.
Meanwhile, officials said an election planned for later this month has been postponed to 7 July.
Earlier, a delegation from the International Criminal Court (ICC) has arrived in Libya to try to secure the release of a four-person team detained after visiting Saif al-Gaddafi, the jailed son of the former leader.
A Libyan official said Australian lawyer Melinda Taylor, who was part of the team, is being investigated on suspicion of spying.
The government said the fighting in Kufra began after members of the Toubou tribe attacked a checkpoint and tried to gain access to a security building nearby and steal their vehicles.
But representatives of the Toubou tribe say they were attacked by security forces - the Deraa brigade - and they have accused the brigade there of trying to "exterminate" them.
Dozens of others were injured in the clashes, while correspondents say the real death toll could be considerably higher.
The BBC's Rana Jawad in Tripoli says much of the fighting is believed to be related to a turf war over smuggling routes used by tribes in the city.
Members of the national army are said to be stationed at the airport in Kufra and are not getting involved, our correspondent adds.
A local security official said shops and schools in Kufra are closed, and electricity has been cut off from the city.
The Deraa brigade is part of the defence ministry, overseeing a shaky truce struck earlier this year after deadly clashes at the time between the Toubou and another tribe.
They were sent to the town after ethnic fighting between the Toubou against the rival Zwei ethnic group in February.
The ICC has meanwhile confirmed that a delegation had arrived in Tripoli to "negotiate with the Libyan authorities and the prosecutor general for the [ICC] team's release".
On Saturday, the ICC said in a statement that the four-person team had been held after a meeting with Saif al-Gaddafi on Thursday, and called for them to be freed.
But Ahmed Jehani, the Libyan envoy to the ICC, told AFP that only two of the four, Ms Taylor, and her Lebanese interpreter, Helen Assaf, were in detention, while the two others - Spaniard Esteban Peralta Losilla and Russian Alexander Khodakov - stayed of their own accord.
"Melinda was arrested because she was caught exchanging papers with the accused Saif al-Islam," he said, adding that Ms Assaf was being held as an "accomplice."
The ICC wants to try Saif al-Islam, 39, for his role in trying to crush the uprising last year which resulted in the toppling and killing of Muammar Gaddafi.
Libya's interim government has so far refused to hand him over for trial in the Netherlands - the seat of the ICC. Libya has insisted he should be tried by a Libyan court.
Also on Sunday, officials announced that the country's election for a constitutional assembly originally set for 29 June had been postponed to 7 July because of "logistical and technical" issues.
At a news conference, the president of the electoral commission, Nuri al-Abbar, said the "very short time" it had been given to prepare for the elections had not been enough, "especially for a country that hasn't seen elections for almost half a century".