A World War Two bomb containing 290lb of “high explosives” has been found in Portsmouth harbour. The item was discovered by a dredger in the water at about 03:00 GMT, the Royal Navy has said.

Specialist divers at the scene said the bomb posed a “very serious threat”. It was therefore towed out to sea and detonated.

All ferries were stopped and trains between Portsmouth and Southsea station and Portsmouth Harbour were suspended during this time, but have since started running again. There were also extensive road closures in the area, affecting access to Gunwharf Quays.

What was the item and how was it found?

The Royal Navy said the device, believed to be a German SC250 that weighs 500lb, was removed from the harbour before being “safely” blown up in the sea off the Isle of Wight.

Lt Mike St Pierre, the officer leading the bomb disposal team, had said: “Despite being old, these devices can pose a very serious threat.”

Dredging is being carried out to deepen and widen a four-mile (7km) channel to allow the navy’s new 65,000-tonne aircraft carriers to dock. Several devices have been found in the harbour since work started in September.

The most recent discovery was a British-made Armstrong Whitworth device found in the early hours of Friday morning, the Royal Navy has said.

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