A bomb destroyed the department of military intelligence in the eastern city of Benghazi early Wednesday, a Libyan security source said.
"The department of military intelligence was bombed," a senior security officer had told AFP earlier, adding that the level of damage to the two-storey building suggested it was hit by an improvised explosive device. A later report by MENA said the bomb completely destroyed the building.
Adjacent buildings were also touched by the dawn blast, he added.
"The incident did not result in injury to any of the guards of the residents of neighbouring buildings," said the official who did not wish to be named.
The identity of the attackers, he said, remains unknown.
Khaled Haidar, spokesman for the director of national security in Benghazi, told AFP that the eastern city has witnessed a series of security breaches over the past week.
These included the discovery and neutralisation of a bomb outside the iconic Tibesti hotel on Sunday.
Friday saw a hand grenade hit the appeals court and a rocket punch the outside wall of the main prison. Both incidents caused only minor material damage to the buildings targeted, he said.
Also on Friday, Haidar added, security forces diffused two time-bombs planted by the office of national security in Benghazi.
The Mediterranean city of Benghazi is the cradle of the revolt that toppled long-time dictator Moamer Kadhafi last year.