The U.S. and five European allies have expressed concerns about growing tensions near the Libyan oil terminal of al-Zueitina and are calling for rival factions to avoid damaging the country's energy infrastructure.

In a joint statement released by the French government, France, the United States, Britain, Italy, Germany and Spain threw their support behind Libya's UN-backed government, saying the country's energy installations should return under government control without condition or delay.

The statement said "the government of national accord must work with the National Oil Corporation to relaunch oil production in order to rebuild Libya's economy."

Libya announced last month the reopening of the country's vital oil terminals after 18 months of closure, despite threats by a rival military commander that his forces could target tankers entering Libya's territorial waters.