Discontent in loyalist communities is "growing" over the Northern Ireland protocol, a senior police officer has warned.

More graffiti as well as low-level intelligence and social media monitoring have provided early pointers, but feedback is not causing the force significant concern, the Police Service of Northern Ireland said.

The PSNI is braced for more street protests over disruption to trade from the rest of the UK once the coronavirus emergency and lockdown restrictions ease.

Assistant Chief Constable Mark McEwan said: "We are seeing signals, there are signal incidents that have happened, particularly in recent days.

"We are starting to see graffiti, we are picking up social media sentiment of a growing discontent, particularly within the Protestant/loyalist/unionist community."

Northern Ireland is continuing to follow some of the EU's rules despite Brexit, to prevent the establishment of a hard border on the island of Ireland.

Hauliers have faced difficulties transporting stock to Northern Ireland from the rest of the UK.

Mr McEwan said the end of the three-month grace period on 31 March, for supermarkets transporting goods and requiring parcels sent to Northern Ireland from the rest of the UK to include customs declarations, is an important date.

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Unless a political solution is found, that could see some items become unavailable in Northern Ireland, or become more costly.

Mr McEwan told the Northern Ireland Affairs Committee of MPs: "That will focus people's minds, I believe, in terms of how Northern Ireland looks and feels for certain members of our community."

Northern Ireland's coronavirus lockdown has been extended until 5 March.

Mr McEwan added: "If we get to the point where we don't have such stringent restrictions, where people are not as worried about the health crisis, we may see that manifest in the likes of protests, and we are prepared for that."

He said intelligence on the unionist community is not causing significant concern but it is something the force is monitoring.

"Were we not in this current environment around the pandemic we would probably see a more visible outworking of that on the streets of Northern Ireland," he added.

The Northern Ireland protocol is designed to allow the region to follow the EU's customs rules and has caused delays at the ports because of new declarations and checks.

The DUP has been vociferous in opposition to the protocol's operation. The party's North Antrim MP Ian Paisley said there is "anger and bitterness" in the communities he represents.

He told the committee: "Some sections are starting to sense that they are sitting on a powder keg."

Claire Hanna, SDLP MP for South Belfast, said it is proper that the senior officer be measured in his comments. She added: "We do not need any trouble at a very difficult time."

The end of the transition period has produced deep-seated structural problems which will not be quick to resolve, the British Road Haulage Association warned.