A caller claiming to represent Óglaigh na h'Éireann said its volunteers had "breached security" at the PSNI station and planted a "semtex device."

The security alert at the heavily fortified police station began on Monday afternoon when the device was discovered.

Students from the nearby North West Regional College had to be evacuated from their classrooms while British Army technical officers examined the object.

A PSNI spokesperson said a number of items were taken away from examination after the security alert.

It is the first time the group has claimed responsibility for an attack in the North West.

The group have previously claimed responsibility for a number of attacks in the Belfast area and have been linked to bomb attacks in Fermanagh.

The Óglaigh na h'Éireann spokesperson also said more attacks in Derry were likely.

"We will strike again when and where we choose," he said.

The caller also called on republicans not to provide information to the PSNI. "We call on our former comrades in the Provisionals not to fall into the trap of becoming informers as some have asked them to do."

In its 19th report, the Independent Monitoring Commission, the body appointed to monitor the activities of paramilitary groups, said devices used by a number of dissident republican groups contained a small amount of Semtex. The Czech-made explosive was widely used by the IRA during the Troubles.

The name Óglaigh na h'Éireann is used by several republican groups but it believed the group which claimed responsibility for the Strand Road attack emerged after a split in the Continuity IRA. It's also believed it has recruited a faction of the Real IRA following a split in that organisation.