Armed protesters have stormed the eastern Libyan oil port of Zueitina in an attempt to stop export operations, a witness has said.
The raid on Tuesday at the port, 850km east of Tripoli, came hours after workers temporarily suspended a strike and resumed production at oilfields that pump to the terminal.
It was not immediately known what the protesters wanted, but an engineer working at the port recognised them as being part of a group of civilian demonstrators who shut down the terminal for several weeks earlier this year demanding jobs.
"The group arrived and asked that operations be shut down," the engineer told the Reuters news agency by phone.
"A ship bound for Italy was being loaded with crude and I had to negotiate with them to allow the loading to continue.
"It was difficult to convince them but the ship is being loaded. All other export activities are shut down."
A senior Libyan oil industry source confirmed the disruption and said export operations were affected.
The incident occurred just hours after workers at Libya's Zueitina Oil Company suspended their strike that had shut down oilfields and halted operations at the Zueitina terminal, demanding a change in management relating to a dispute over work conditions.
The engineer told Reuters earlier production was resuming at those fields.
Saad al-Fahri, deputy chairman of the Libyan oil workers' union, said that the striking workers had agreed to end their protest until the end of the fasting month of Ramadan, expected on August 8 or 9, after which they would review their position.
Operations had resumed at the Zueitina terminal on Monday, but only oil stored at the port was being exported.
Zueitina is a relatively small producer, pumping between 60,000 and 70,000 barrels of oil and condensate, a light form of crude, per day.
The company's terminal, however, has the capacity to handle about 20 percent of Libya's crude oil exports.
Closing down oil exports would affect other fields that pump to Zueitina's export terminal, such as Abu Attifel, operated by Mellitah - a joint venture between Libya's National Oil Corporation and Italy's Eni.
Protests and strikes at various facilities have repeatedly lowered Libya's oil output, which returned faster than expected to pre-war levels of around 1.6 million barrels per day (bpd).
The oil industry source said that before the latest disruption, output had stood at 1.36 million bpd.
As well as cutting OPEC member Libya's oil output, the Zueitina workers' protest has caused shortages of gas supply to power stations. Several Libyan cities have seen nearly daily power cuts for several hours in the last few weeks.
Authorities are trying to limit the cuts during Ramadan.
Oil Minister Abdelbari al-Arusi said on Sunday that he had met representatives of the protesting workers in Tripoli and hoped a solution would be found soon.
The Zueitina engineer said Arusi had sent a letter to the protesters saying he would implement some of their demands after Ramadan.
Oil Ministry officials could not be reached immediately for comment.