US Navy Seals boarded and took control of an oil tanker that had loaded crude at a rebel-held port in eastern Libya and escaped to sea, the Pentagon said Monday.

No one was hurt "when US forces, at the request of both the Libyan and Cypriot governments, boarded and took control of the commercial tanker Morning Glory, a stateless vessel seized earlier this month by three armed Libyans," Pentagon press secretary Rear Admiral John Kirby said in a statement.

The operation was approved by President Barack Obama and was conducted in the early hours of Monday (just after 0200 GMT) "in international waters southeast of Cyprus".

The Morning Glory "is carrying a cargo of oil owned by the Libyan government's National Oil Company. The ship and its cargo were illicitly obtained from the Libyan port of Al-Sidra," the statement read.

The US Seals operated from the USS Roosevelt, a guided missile destroyer, which "provided helicopter support and served as a command and control and support platform".

Sailors from another destroyer, the USS Stout, boarded the tanker and prepared to sail it to an unnamed port in Libya, the statement read.

The Morning Glory, which last week slipped through a Libyan naval blockade of the eastern port of Al-Sidra -- controlled by rebels seeking autonomy from the authorities in Tripoli -- reportedly loaded some 234,000 barrels of crude.

In Nicosia, the Foreign Ministry said Monday that the tanker had been immobilized in international waters southeast of Cyprus since Saturday.

"Close to midnight on Sunday, the Cypriot authorities were aware of it moving in a westerly course, always within international waters," said the ministry.

Cypriot vessels "were deployed in monitoring the tanker's course. The vessel stopped once more 18 nautical miles south of Limassol," a city in southern Cyprus.

However the tanker did not ask for authorization to moor in a Cypriot port.

Soon after Cypriot officials were notified that the tanker "was placed under the control of the US Navy and is being escorted by US Navy vessels on a westerly course."

While the statement says nothing about Cyprus asking US forces to intervene, the ministry previously said that Libya had asked for help in the return of the stolen oil, and that Nicosia was monitoring the tanker's whereabouts.

The Morning Glory originally was a North Korean-flagged ship, but Pyongyang on Wednesday denied any responsibility.

The ship was operated by an Egypt-based company that was allowed to temporarily use the North Korean flag under a contract with Pyongyang, North Korean state news agency KCNA said.

Pyongyang had "cancelled and deleted" the ship's North Korean registry, as it violated its law "on the registry of ships and the contract that prohibited it from transporting contraband cargo".

The loading of the Morning Glory and its escape to sea marked a major escalation in the struggle between Tripoli and the rebels, and triggered the ouster Tuesday of liberal-backed premier Ali Zeidan, who fled the country.

Zeidan, an independent, proved incapable of bringing to heel the former rebel militias who have carved out their own fiefdoms since the 2011 uprising that toppled the dictatorship of Moamer Kadhafi.