The poorest continue to lead demonstrations in one of the most disadvantaged parts of the country.
Both sides have stopped short of withdrawing forces from the frontline, as demanded by the truce.
Tripoli's government enjoys the support of Russia, France, Egypt, the United Kingdom and Saudi Arabia, among others.
The attack came as the United Nations was brokering a truce in the capital Tripoli, where the eastern-based Libyan National Army (LNA) force launched a surprise attack in April.
"The air strike resulted in 43 killed and 51 wounded. This is only an initial toll of casualties."