Eastern-based Libyan forces have intercepted a Turkish ship under a Jamaican flag heading to the port of Misrata in western Libya, their spokesman said on Monday.
Turkey is the main foreign backer of the internationally recognised Government of National Accord (GNA), in the west, which has for years been fighting the eastern-based Libyan National Army (LNA).
LNA spokesman Ahmed Al Mismari added that the commercial cargo ship, Mabrouka, had 17 crew, including nine Turkish nationals, and containers that had not yet been inspected. LNA naval forces stopped it near the eastern port of Derna, he said.
A spokesperson for Turkey's Ministry of Foreign Affairs was not immediately available to comment.
The GNA and LNA signed a ceasefire deal in October and the United Nations has been pushing a political dialogue aimed at elections next year as a solution to Libya's long-running conflict.
But both sides have stopped short of withdrawing forces from the front line, as demanded by the truce. On Sunday LNA forces seized a military camp in southern Libya, has further pushed the truce.
Earlier on Monday, Mr Mismari accused Turkey of continuing to supply arms and fighters to the GNA.
European Union foreign ministers also accused Ankara of failing to help resolve a dispute over natural gas resources in the eastern Mediterranean, but they left any decision on retaliatory sanctions for an EU summit on Thursday.
The 27 ministers, who were tasked to evaluate the grounds for economic sanctions on Turkey, did not go beyond agreeing Turkey had aggravated tensions since October, when EU leaders voiced a threat to impose punitive measures in December.
The EU cites Turkish exploration in contested waters, a decision to re-open part of a town in disputed territory in Cyprus and a row with Germany over a UN arms embargo on Libya as evidence that Turkey is no longer a reliable partner.