The Arctic Sea cargo vessel and the Russian warship escorting it are believed to have left the Canary Islands, a source at the Las Palmas port said on Thursday according to RIA Novosti.
"The cargo vessel and the warship disappeared from our radars, which cover an area with a radius of 25-30 nautical miles," he said.
A Russian military official said on Wednesday that the Ladny frigate would provide security for the Arctic Sea until it was handed over to its owners.
The Arctic Sea was originally expected to dock at the port of Las Palmas, the capital of Spain's Canary Islands, to be handed over to its Maltese owners on September 18. However, the Maltese authorities unexpectedly refused to take part in the handover of the ship, and the vessel remained anchored 25 kilometers offshore.
The Maltese-flagged and Russian-crewed vessel, listed as carrying lumber from Russia to Algeria, was reportedly boarded by a group of eight men on July 24. Officials later said it had disappeared in the Atlantic. It was freed off Cape Verde on August 16 by the Ladny.
The ship has been the focus of media speculation, with some reports speculating it was carrying Russian S-300 air defense systems to Iran or Syria. Moscow has denied the reports.
A spokesman for the Investigative Committee of the Russian Prosecutor General's Office said last week that investigators who searched the ship had not found any "compromising" cargo on board.