Gunmen on Saturday shot dead a former member of Moamer Kadhafi's security services in eastern Libya, in the latest violence to hit the region, an official said.
Unidentified men with assault rifles gunned down Fares al-Zarruk in a busy street in the centre of Derna, a town that has been hit by mounting deadly unrest, the security official said.
Zarruk died on the spot and his attackers fled, the official told AFP.
Also on Saturday, an Iraqi university lecturer went missing in Derna and was presumed kidnapped, another official told AFP, speaking on condition of anonymity.
"The family of Professor Khaled Hamid Heidar lost all contact with him on Saturday afternoon," said, calling the disappearance "apparently a kidnapping".
"All Iraqi teachers in the town are fearful of meeting the same fate," he added.
The abduction, if confirmed, follows the reported execution of a Libyan prisoner in Iraq last week.
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Another Libyan sentenced to death is among nine Libyans currently held in Iraqi prisons.
However Sleiman Fortia, who heads a support group for Libyan prisoners abroad, said there was no link between the lecturer's disappearance and the Libyans in Iraq.
He deplored what he called a lack of government interest in the fate of the prisoners in Iraq, saying two of the Libyans had been freed but were unable to come home because the Libyan authorities had not intervened.
Since last Saturday a judge, a tribal chief and two traffic policemen have been killed in Derna near Libya's second city Benghazi, the epicentre of the 2011 uprising that toppled Kadhafi's regime.
Most of the violence is blamed on Islamists whose influence has grown since the revolt in which Kadhafi was also killed.
Some of them rose from the ranks of rebels who helped overthrow and kill the veteran dictator.
Since the end of the uprising the ex-rebels have banded into militias, carving their own fiefdoms in a country awash with weapons looted from Kadhafi's arsenal.
The government has struggled to stamp its authority and repeatedly called the ex-rebels to lay down their weapons or integrate into the armed forces, to no avail.