The owner of the Pumphouse Pub in the Maritime Quarter told ITV News that armed police are on the scene blocking entry to the marina.
There's a police helicopter and armed police outside blocking the road. We haven't been asked to close the pub, but there are police and dogs on leads outside and nearby. The marina is also blocked off and no boats are allowed in or out.
The Grape and Olive restaurant at the top of the Meridan Tower has tweeted to say it's closed due to an incident.
Restaurant closed due to incident all bookings cancelled sorry for any inconvenience
More top news
A new report has estimated that101,000 carers in Wales are currently supporting loved ones with cancer.
Helen Plint has the latest forecast for Wales.
The Labour conference has voted to give the Welsh party more autonomy, despite opposition from supporters of Jeremy Corbyn.