The US has taken control of a tanker full of oil loaded from a rebel-held port in Libya, the Pentagon says.
The raid by Navy Seals took place in international waters south of Cyprus, said spokesman Rear Adm John Kirby.
The Morning Glory’s evasion of a naval blockade at the eastern port of Sidra prompted Libya’s parliament to sack Prime Minister Ali Zeidan last week.
In a separate incident on Monday, an attack on an army base in the city of Benghazi killed several soldiers.
A bomb went off as people were leaving a graduation ceremony for officers, police said.
The Morning Glory was the first vessel to have loaded oil from a rebel-held port since a separatist revolt against the central government in Tripoli erupted in July 2013. It is not clear where the tanker was headed.
Adm Kirby said the operation had been authorised by President Barack Obama and that no-one had been hurt.
“The Morning Glory is carrying a cargo of oil owned by the Libyan government National Oil Company. The ship and its cargo were illicitly obtained,” he said, adding that it would now be returned to a Libyan port.
The vessel was flagged in North Korea but officials in Pyongyang said it had been deregistered because of the incident.
It was said to have been operated by an Egyptian company.
The BBC’s Rana Jawad in Tripoli says the US move is likely to act as a deterrent to any further attempts to illicitly buy oil from the rebel-controlled ports.
She says that after backing the 2011 rebellion against Muammar Gaddafi, the US does not want Libya to become a failed state.
The Libyan government is still struggling to assert its authority on rebel groups that helped to overthrow Col Gaddafi.