Libya's deputy intelligence chief Mustafa Nuh was abducted on Sunday in Tripoli, a security official told AFP, as tensions ran high in the capital following deadly violence over the weekend.
"The vice president of intelligence was abducted shortly after his arrival in Tripoli from a trip abroad," said the official, who declined to be named.
Contacted by AFP, an intelligence source confirmed that Nuh had "disappeared" but did not elaborate.
Private channel Libya al-Ahrar reported he was abducted, but it did not cite any sources for its report.
There was no immediate claim for the abduction, which came as Tripoli began a three-day strike to mourn dozens of people killed in clashes at an anti-militia protest -- the deadliest violence in the capital since the 2011 uprising.
At least 43 people were killed and more than 450 wounded in the fighting, according to the health ministry.
The violence erupted on Friday when demonstrators protesting against unruly militias in Tripoli were fired upon from a base of ex-rebels in the capital and raged overnight and into Saturday.
The weak central government has struggled to rein in former rebel brigades that helped end Moamer Kadhafi's 40-year dictatorship but have since grown into increasingly menacing militias.
Libyan Prime Minister Ali Zeidan was himself abducted for several hours by gunmen in October before being released unharmed.
A security chief claimed responsibility for the abduction and said he was "proud" of it.