"Non-flagged ships will be checked for documents. These are the types of marine vehicles that typically carry migrants," the source told RIA Novosti.
The EU source specified that no identity checks would be carried out during vessel document verification.
Operation Sophia encompasses Italian, French, German, British and Spanish warships, including Italy’s Cavour C 550 aircraft carrier and France’s Courbet F 712 stealth frigate.
Three additional Belgian, British and Slovenian warships are expected to join the operation by late October.
The first phase focused on collecting information on human traffickers, using vessels and aircraft deployed in international waters. The second phase of the naval operation authorizes boarding, search, seizure and diversion of ships found to be used for human trafficking.
EU border agency Frontex estimates that some 630,000 migrants and refugees have crossed the Mediterranean to Europe since the beginning of 2015. Almost 3,000 people are reported to have died or gone missing en route.