A LIBYAN air force colonel was shot dead in the eastern city of Derna, a military spokesman said.

Unidentified assailants shot Colonel Fathi al-Omami on Monday evening as he visited a shop he owned.

"A car was apparently waiting for him and those inside shot him," said Ali Sheikhi, spokesman for the army chief of staff's office.

Residents carried him to a nearby hospital, where he was pronounced dead.

Violence has worsened in Libya in recent months as the government tries to impose its authority on militias that helped overthrow Muammar Gaddafi in 2011. Islamists, who were suppressed under Gaddafi, have also come to the fore.

Derna is known across the region as a recruitment centre for militants who have joined wars in Iraq, Afghanistan and Syria.

In Tripoli, bombs exploded in a military vehicle and three cars used by people working for the military police, a government spokesman said. No one was hurt.