Three teenage migrants have been charged in Malta after "hijacking" an oil tanker, which is considered a terrorist activity under Maltese law.

One has been named as Abdalla Bari, 19, from Guinea. Two others, 15 and 16, are from Guinea and Ivory Coast and, as minors, cannot be identified.

All three deny the charges. They face up to 30 years in jail if found guilty.

The tanker, Elhiblu 1, had more than 100 migrants on board. All have been taken into custody.

The migrants had been rescued by the ship but reportedly hijacked it on Wednesday after being told they would be returned to Libya.

They are alleged to have told the captain to head north towards Europe instead.

A patrol vessel later stopped the tanker from entering Maltese territorial waters and a special operations team was dispatched to board and secure the vessel, the Armed Forces of Malta (AFM) said in a statement.

Malta's Prime Minister Joseph Muscat has said all international rules will be followed as police investigate the incident.

The latest incident comes as the European Union says it is ending navy patrols in the Mediterranean. The EU says the decision to suspend Operation Sophia from September follows a request by Italy. (BBC)