TRIPOLI (REUTERS) - More than 40 people were killed on Thursday in an explosion at an army depot in southern Libya after locals tried to steal ammunition, and four soldiers died in other violence in the restive east, officials said.

The incidents highlighted the turmoil in Libya, where the government is trying to restore order in the oil-producing country, which is awash with weapons after the 2011 ouster of Muammar Gaddafi.

The blast in Brak al-Chati, near the main southern city of Sabha, happened after a group of 43 locals and Africans were entering the army depot to steal ammunition, a security official said. The casualties could rise further as the depot was still on fire and people might be trapped inside.

Libya's nascent military is struggling to secure army bases and curb Islamist militants, militias and gangs who fought in the uprising against Gaddafi but refuse to disarm and control parts of the country.

The four soldiers were killed in Benghazi as clashes erupted between army special forces and militant Islamists of the Ansar al-Sharia group, officials said.

The trouble started when soldiers stopped a car loaded with weapons, explosives and large amount of money. "Three soldiers were killed in clashes with Ansar al-Sharia," Mr Wanis Bukhmada, commander of the special forces in Benghazi, told a news conference. He later told Reuters: "We will defend Benghazi."

Another soldier was assassinated by unknown gunmen in the morning in another part of the city, a security source said.

Fighting initially started on Monday between army special forces and members of the Ansar Sharia in Benghazi, Libya's second-largest city. At least nine people were killed before the Islamists retreated from their main base. Three more soldiers were killed on Wednesday.