(BBC) - Car bombs have been detonated in two eastern Libyan cities, leaving at least five people dead and many more injured, reports say.

The first attack on a busy road in Tobruk is thought to have killed at least one person, possibly a bomber.

Another four died when a car blew up outside an air base in Al Bayda.

Libya has been in a state of flux since Muammar Gaddafi was overthrown in 2011, with disparate tribes, militias and factions fighting for power.

The Tobruk blast appears to have taken place close to the city's intelligence headquarters.

Eyewitnesses said at least 21 people were injured. Five cars at the scene were badly damaged.

It is not clear whether either blast was a suicide attack or an improvised explosive device.

Libyan air force planes were seen flying over Tobruk after the attacks.

Army spokesman Mohammed Hegazi, quoted by the Associated Press news agency, blamed the attacks on IS-linked militants in the nearby town of Derna.

Three activists kidnapped earlier this month were found beheaded in Derna on Tuesday.

Tobruk is home to Libya's parliament, which moved there because of security fears in the capital Tripoli, and whose legitimacy is disputed. Libya's constituent assembly, tasked with drawing up a new constitution, is based in Al Bayda.

Libya's Supreme Court last week declared the parliament unconstitutional but the court's own impartiality is in doubt.

Politicians in Tobruk have repeatedly alleged that Tripoli's courts, judges and their families have been under threat by the coalition of armed groups that controls the capital.