BENGHAZI: Military forces loyal to Libya's eastern government said on Tuesday they had taken control of two key neighbourhoods in Benghazi, building on gains made against Islamist fighters over the previous three days.

The military said it had full control of the districts of Boatni and Laithi and claimed advances in several other areas. A hospital source said 20 people had been killed and 45 wounded in the latest clashes.

The eastern city of Benghazi has seen some of the worst violence in the conflict that has plagued Libya since Muammar Gaddafi was toppled in an uprising five years ago.

The violence escalated when military commander Khalifa Haftar launched a campaign in 2014 against Islamists and other armed groups, with the factions taking up entrenched positions in Benghazi's streets.

On Tuesday residents celebrated the army's advances by sounding car horns and setting off fireworks. Some returned to their homes for the first time in months to check for damage.

Haftar's Libyan National Army is loyal to Libya's eastern government, which has received international recognition but is opposed by a rival government based in Tripoli.

A unity government nominated under a United Nations-backed plan is trying to win support within Libya, but its progress has been hindered by political arguments including what role Haftar could have in a future national army.

Libya's eastern parliament rejected an initial unity government line-up last month and has repeatedly delayed voting on a revised proposal, pushing back a vote once again on Tuesday.

Islamist fighters have exploited a security vacuum to expand their presence in Libya, with militants loyal to Islamic State establishing control in the coastal city of Sirte and a presence in several other cities, including Benghazi.

In a separate development on Tuesday, the mayor of the western city of Sabratha said military brigades there had attacked several buildings housing suspected Islamic State militants.

Hussein al-Thwadi said militants at one of the sites had fought back, and that four brigade members had been killed and five injured.

On Friday a US air strike against a suspected Islamic State training camp in Sabratha killed nearly 50 people. Serbia's government said two of its diplomats who were kidnapped in Libya in Benghazi in November also died in the strike.