Several hundred loyalist protesters gathered in south Belfast on Thursday evening before marching along Donegall Pass towards the Sandy Row area.
The parade was not referenced on the Parades Commission website as a scheduled event and was held in protest against the Northern Ireland Protocol.
A number of bands took part in the march, as those in attendance held placards expressing disapproval of the protocol and demanding Prime Minister Boris Johnson “triggers Article 16”.
Other posters read. "EU out of Ulster”, along with “Boycott Irish/EU goods”.
A number of people also held signs saying: “Political policing must stop” and “Defund the BBC”.
The protocol was designed to prevent a hard border on the island of Ireland, with Northern Ireland continuing to follow EU trade rules.
There are tensions over the Northern Ireland Protocol, with unionists claiming the additional checks on goods are placing a border down the Irish Sea.
There have been demonstrations against the Protocol as well as legal challenges to it.
While there was a significant PSNI presence during the march, the protest on Thursday evening is believed to have passed off peacefully.
During a visit to Northern Ireland, Labour leader Sir Keir Starmer accused the Prime Minister of having "betrayed" the people of Northern Ireland.
The Labour leader was speaking during two days of official engagements in the region accompanied by shadow secretary of state Louise Haigh.
Reflecting on having worked in Northern Ireland for six years with police in the early 2000s, Sir Keir said he learned the importance of trust and the role of the UK Government as an honest broker, bringing communities together.
Sir Keir told the PA news agency in Belfast that Boris Johnson had "not been straight about the consequences" of the Protocol.
"He is now pretending it is someone else's problem, and in Northern Ireland that won't wash," he said.
"There has to be a practical way forward on this, I think there is a practical way forward if the parties are flexible and negotiate, but the most important thing is trust.
"There is a positive future here but it does require the British Government to properly understand its role, and I think that this Prime Minister, Boris Johnson, has betrayed the people of Northern Ireland by not properly honouring that (the UK Government being an honest broker), and the words that have been used in pretty well every meeting I have had here in Northern Ireland is a lack of trust in the Prime Minister as an honest broker.
"That is a massive missing piece."
In a statement, PSNI Chief Inspector Gavin Kirkpatrick said: “Police are in attendance at a protest gathering and un-notified procession in the Donegall Pass area of south Belfast this evening.
“Organisers of parades/processions are required to give formal notification of their intentions, which was regrettably not provided or forthcoming.
"We have issued a number of warnings and an evidence-gathering operation is in place.
“We will review footage gathered and consider any suspected breaches of the Public Processions (NI) Act 1998 and offences in respect of the Health Protection (Coronavirus, Restrictions) Regulations NI 2021."