New clashes between the Libyan army and Islamists erupted in the eastern city of Benghazi early on Wednesday, wounding several people, security sources and residents said.

Libya's military is struggling to curb Islamist militants and militias who fought in the 2011 uprising against Muammar Gaddafi but refuse to disarm and control parts of the OPEC producer.

Fighting broke out on Monday between army special forces and members of the Ansar Sharia in Libya's second-largest city, killing at least nine people before the Islamists retreated from their main base.

Fresh gun battles could be heard in three parts of the port city after midnight, residents said. The Ansar Sharia were also amassing forces outside Benghazi where the army was rushing reinforcements in a convoy, city security sources said.

The new violence had started when members of the Ansar threw a grenade at a patrol of special forces, a security source said.

The security situation has sharply deteriorated in the past few months in Benghazi where Islamists run their own checkpoints and assassinations are part of daily life.

Most countries have closed their consulates in Benghazi, home to several oil companies. Some foreign airlines also have stopped flying there.

Ansar al-Sharia was blamed for the attack on the U.S. consulate in Benghazi a year ago when the U.S. ambassador and three other Americans were killed.

The chaos in Libya is worrying its neighbours and the Western powers that backed the uprising which led to the fall of Gaddafi two years ago in one of the Arab Spring revolts.

Hoping to co-opt former fighters, the government hired militia groups to provide security. But they remain loyal to their commanders or tribes, and often clash in disputes over territory or personal feuds.

Oil exports are down to a fraction of capacity due to seizures of oilfields and ports by militias, tribesmen and civil servants demanding more political rights or higher pay.