Britain on February 2 condemned threats to port workers implementing controversial post-Brexit trade checks in Northern Ireland, calling for clear heads to ease fears of an upsurge in sectarian tensions but pointing blame at the EU.

Checks were suspended at Belfast and Larne ports late on February 1, and the European Commission said it had told its staff working at two border posts in the British province to stay away.

The development comes just over a month into new trading arrangements after Brexit took full effect, and warnings it could stoke lingering community tensions in Northern Ireland.

Prime Minister Boris Johnson said EU moves last week to restrict vaccine exports to the UK province, amid controversy over jab deliveries but which were swiftly abandoned, had “undermined” its special post-Brexit arrangements and “provoked concern”.

“What is needed is urgent action from the EU to resolve outstanding problems with Protocol implementation,” he said on Twitter, while reiterating that “Northern Ireland’s place in the UK will be protected and strengthened”.

The regulatory animal-based food checks were dropped on the orders of Northern Ireland’s Department of Agriculture, Environment and Rural Affairs.

At Larne Port, 12 staff were pulled from duties after “an upsurge in sinister and menacing behaviour in recent weeks”, the Mid and East Antrim Borough Council said.

Hardcore unionists have been blamed for graffiti criticising the Northern Ireland Protocol and describing port staff as “targets”, it added.

Attempts also seemed to have been made to collect information on employees, including vehicle registration plates, in acts of intimidation recalling the darkest days of “The Troubles” in Northern Ireland, media reported.

But officers are said to have no evidence that intimidation efforts are being organised by the main loyalist paramilitaries active in the province.

Police Service of Northern Ireland (PSNI) Assistant Chief Constable Mark McEwan told the BBC that “individuals or small groups of people” were responsible.

Lorries were still passing through the port at Larne, but police patrols have nevertheless been stepped up, while Northern Ireland’s leaders were due to talk to UK and EU ministers on February 3.