German airline Lufthansa and its subsidiary Austrian Airlines have halted flights to Libya indefinitely due to security concerns after a bomb at Tripoli airport two weeks ago, a Lufthansa spokesman said.

In March, a bomb exploded on the main runway at Tripoli, highlighting the deteriorating security situation in the North African country.

Lufthansa, Austrian, Italy's Alitalia and British Airways suspended flights immediately and had left open whether or when operations would resume.

Alitalia said it would continue to suspend flights until April 15, after which the situation would be reviewed.

A Lufthansa spokesman said: "We've decided to suspend flights to Tripoli indefinitely due to security and operational reasons."

Libyan carriers are banned from flying to the European Union for security reasons. They have to rent a plane and crew from an airline allowed to fly into the region, so the resumption of regular European flights is of vital economic importance.

Libya's government seems unable to control militias who helped overthrow Muammar Gaddafi in 2011 and have recently seized government facilities to make financial and political demands.

In another sign of insecurity, young men blocked the airport road from central Tripoli for hours. Long queues of cars formed until the late evening, witnesses said.

A Reuters reporter saw men burning tyres and holding up banners denouncing the General National Congress (GNC), the parliament which many Libyans blame for their country's bumpy transition since its 2011 uprising.

"We blocked the road because we want security. We are against assassinations in Benghazi," said protester Fawzi Masbah. The eastern city of Benghazi has been hit by almost daily assassinations of army and police officers. - Reuters