Willie Frazer was arrested on Wednesday morning while the home of fellow Ulster People’s Forum member Jamie Bryson was searched by police, it has been reported.
In a post on Mr Bryson’s Facebook page on Wednesday morning it was claimed his home was being “ransacked”.
It was also claimed Mr Frazer is “on his way to Musgrave”.
Police this morning confirmed a 52-year-old male was arrested in the Tandragee Road area of Markethill “on suspicion of public order offences relating to the flag protests”.
Both men have been key figures in the flag protests which have taken place in Northern Ireland for the past three months.
When the News Letter contacted Mr Bryson just before 10am another male answered and confirmed the Forum chair had not been arrested but claimed the house search was “political policing”.
He said: “This is political policing. That this is Matt Baggott under pressure from Sinn Fein and others. Gerry Kelly tweeted last night...” The phone then hung up.
The News Letter also contacted Barrie Halliday of Victims’ Group FAIR who spoke from Willie Frazer’s house on Monday morning.
He said there were about a dozen police involved in the arrest at 9am.
He added: “It’s one of them things. Baggott came out with a speech yesterday so they [PSNI] had to do something I suppose.”
Many of the protests, which have been going on since before Christmas when the city council voted to fly the flag only on designated days, have erupted in violence, particularly in east Belfast.
Loyalist paramilitaries were heavily involved in the disturbances.
At one stage there were nightly demonstrations, but they have been scaled back to Saturday afternoons outside City Hall.
Even though 149 people have been arrested and charged, Chief Constable Matt Baggott has been under increasing pressure from nationalist politicians to take a harder line against the protests.
Almost 150 of his officers have been injured in the disturbances.