Portsmouth Historic Dockyard is to be closed all day and a section of the harbour has been sealed off following the discovery of an unexploded German bomb.
The Royal Navy has issued a statement to say a 500m cordon is in place around the device, which prevented cross-channel ferries from entering and leaving the ferry port.
The device, dating from the Second World War, was found by a dredging barge carrying out work in the harbour before the arrival of HMS Queen Elizabeth - the navy’s new 65,000-tonne aircraft carrier - into the naval base next spring.
The statement adds: ‘Victory Gate is closed to pedestrians. Naval base employees are instead having to enter through Marlborough Gate on Queen Street.
‘A plan is in place to tow the bomb out of the harbour where it will be destroyed in open waters by RN bomb disposal experts.’
Both Wightlink and Gosport ferry services are initially unaffected but towards lunchtime the Gosport Ferry was suspended and a Wightlink spokeswoman said: ‘Wightlink’s Portsmouth-Fishbourne and Portsmouth Harbour-Ryde Pier Head services are being affected following the discovery of an unexploded device in the north of Portsmouth Harbour near the International Ferryport.
‘The 11:47 Wightlink catamaran service from Ryde Pier Head to Portsmouth Harbour is returning to Ryde with its customers.
‘St Cecilia, the 12:00 car ferry sailing from Portsmouth, sailed to Fishbourne as normal but St Clare, the 12:00 sailing from Fishbourne has not left the Isle of Wight.
‘We will update passengers when we have more information.’
Normal ferry services were resumed after the bomb was towed out of the harbour at around 2pm.
It’s the third bomb found in the harbour since September, the first being a British torpedo on September 10 which also resulted in a 500m exclusion zone being put in place. A second 500kg bomb was then blown up in the harbour later in the month.
A spokesman at Portsmouth Historic Dockyard has confirmed the attraction will be shut all day but it will reopen tomorrow.
Britanny Ferries said three of its sailings from Portsmouth were affected - the Normandie to Caen at 8.15am, the Cap Finistere to Bilbao at 11.45am and the Bretagne to St Malo at 8.15pm tonight.
A spokesman said: ‘We are very sorry for the inconvenience this will cause to our passengers on ships awaiting arrival, as well as passengers at Portsmouth Port waiting to depart. As soon as we are given more information regarding the timescale for removing the unexploded ordnance we will inform passengers.’
Brittany Ferry officials say the Queen’s Harbour Master has now given clearance for ferries to come in.
Dave Hartley from Portsmouth Historic Dockyard said visitors were being encouraged to go instead to alternative attractions such as the Royal Marines Museum and that the plan is that the Historic Dockyard will be open again tomorrow.