Most ports in Libya are still able to operate despite the country's rival governments, economic chaos and increasing violence between armed groups, a shipping industry official said on Monday.

Libya is in turmoil as a result of a struggle between forces backing its internationally recognised government based in the east and a rival administration that has taken control of Tripoli, as former rebels who helped to oust Muammar Gaddafi in 2011 have fallen out along political, regional and tribal lines.

Armed forces loyal to the internationally recognised government of Prime Minister Abdullah al-Thinni have been fighting Islamist groups in Benghazi.

"The main ports are all operating except Benghazi for the time being and Derna," Asem Baruni, general manager with Tripoli-based shipping agent Roban Global Maritime, said.

"There is no problem from the manpower side." Baruni said companies had to work with the separate port authorities in areas controlled by the two governments.

"We are dealing with the authorities within the port," he said. "Somehow it is working."

U.N. Special Envoy Bernadino Leon, who has been trying to end the power struggle between the rival governments, has said Libya was on the verge of economic and financial collapse.

Risks to merchant shipping have increased in recent months. In May, forces loyal to Thinni shelled a Turkish ship off the Libyan coast after it was warned not to approach, and one crew member was killed. The vessel was told not to break a ban on approaching the eastern port city of Derna.

"Entering Derna is out of the question for who knows how long," Baruni told Reuters during a visit to London. "It is a forbidden area."

A Libyan warplane bombed a Greek-operated oil tanker anchored off Libya's coast in January, killing two crewmen.

Baruni said for the time being the attacks on ships had not impacted commercial shipping, adding that they were being viewed as isolated incidents.

"If there will be another incident or two that results in deaths and injuries, I am sure there will be some kind of reaction from the (ship) owners," he said.

Islamic State militants, which control parts of Iraq and Syria, took over the city of Sirte on Libya's central Mediterranean coast in stages this year and have now seized the town of Harwa to the east of Sirte. The group has a strong presence in the eastern city of Derna.

Baruni said the situation inside Libya would deteriorate if Islamic State made more gains.

"It will become much worse in a very short time ... if things do not get solved," he said. – Reuters