The Royal Navy warship HMS Diamond will sail to the southern Mediterranean to join an operation aimed at countering arms trafficking.
The Type 45 destroyer left Portsmouth on Wednesday evening and will replace the Royal Fleet Auxiliary ship RFA Mounts Bay during a planned maintenance period.
Meanwhile her sister ship HMS Daring will sail on Friday to the Gulf to support US aircraft carriers launch strikes against Daesh.
Diamond will join Operation Sophia for around two months, which is focused on tackling the human smugglers and arms traffickers who endanger the lives of innocent people. Her focus will be on tackling the movement of arms. She will provide a picture-building capability to help enforce the UN Security Council Resolution prohibiting the trafficking of arms to Libya.
The UK has also played a leading role in the counter-smuggling aspect of Operation Sophia and has committed to building the capacity of the Libyan coastguard, so the Libyans are better able to stop boats in their own territorial waters. Earlier this week HMS Enterprise rescued more than 700 people while serving on the operation.