A Russian tanker that was heading to Malta was seized by military forces in Libya when it allegedly tried to smuggle oil off Zuwara.
The crew, 10 men and a woman, were detained.
The oil tanker Mekhanik Chebotarev was reportedly being filled with oil by smaller vessels out at sea.
Zuwara has no oil terminal, and oil tankers do not normally visit the seas around, with the nearest terminal at Zawiya to the east.
The seizure took place on Wednesday, with reports that naval vessels from Italy and Russia raced to the scene but did not intervene.
Zuwara, whose leaders are nominally part of the Libya Dawn coalition which controls Tripoli, has been a home for Libyan smuggling since the revolution.
More recently, Zuwara has also become a centre of Libya’s massive people-smuggling trade, with tens of thousands of migrants sent to Europe in small boats and the beaches sometimes festooned with those who drown in the attempt.
Earlier this month townspeople held protests against the smuggling gangs.
The seas off Zuwara are presently full of both smuggling boats and NATO warships intercepting them to rescue the migrants on board.