A Royal Marine continues to be questioned by detectives investigating Northern Ireland terrorism connected to two major dissident republican arms finds.

Ciaran Maxwell, 30, from Larne, Co Antrim, was arrested in a pre-planned swoop in Somerset on Wednesday. The operation involved searches at a house and wooded area in south Devon.

In Northern Ireland, officers also searched a number of properties in Larne - near the two forest parks where the weapons dumps were discovered earlier this year.

Maxwell is being detained on suspicion of preparation for acts of terrorism.

While the threat posed by violent dissident republicans in Northern Ireland has been classified as severe for a number of years, in May the UK intelligence services raised the threat level in Great Britain from moderate to substantial.

Two separate hauls of weapons were discovered in Carnfunnock and Capanagh parks within three months of each other.

An armour-piercing improvised rocket and two anti-personnel mines were among the cache recovered at Capanagh in May.

Several pipe bombs, magazines and ammunition for an assault rifle as well as bomb component parts and command wires were also concealed in barrels in purpose-built holes in woodland.

In March, bomb-making items were found at nearby Carnfunnock Country Park.

Police said four barrels were unearthed at Carnfunnock - two barrels were empty but two contained a variety of bomb-making components, including wiring, toggle switches, circuit boards, partially constructed timer power units, ball bearings and a small quantity of explosives.

Larne is predominantly unionist/loyalist in community make-up, so the discovery of the finds led to some initial speculation that they could be linked to loyalist paramilitaries. However, after assessing the nature of the weaponry, police concluded they most likely belonged to dissident republicans.

The extremists intent on bringing about a united Ireland by violent means are small in both number and capacity compared with the republican paramilitary organisations of the Troubles, but they retain the ability to launch deadly if sporadic attacks on the security forces.

Since 2009 dissidents have murdered two soldiers, two policemen and two prison officers in Northern Ireland.

Police activity was continuing in Devon on Thursday.

Searches were being carried out at a property in Exminster by the Metropolitan Police Service's Counter Terrorism Command and local uniformed officers.

Further searches were taking place in the nearby Powderham New Plantation wooded area, which had been cordoned off by Police Service of Northern Ireland officers.

Detective Chief Inspector Antony Hart, of Devon and Cornwall Police, said: "Local officers will be in the Exminster area and will be speaking to residents to help offer reassurance.

"Searches are expected to continue throughout the weekend at the property in question. Searches are also continuing at the nearby wooded area.

"Road closures will be in place on some of the minor roads surrounding the wooded area and are also expected to remain in place throughout the weekend.

"We apologise for any inconvenience this will cause and thank the public for their patience."