The loyalist feud has escalated dangerously with the forced evacuation of LVF-linked families from an east Belfast estate by the rival UVF.
Scores of men, thought to be associated with the UVF, last night remained on the streets of Garnerville to ensure that families forced out at the weekend did not return.
Residents in the Glenlea area, near the PSNI training college, say the UVF action followed their requests for action to halt drug-dealing and other LVF activity.
Local Presbyterian minister Rev Richard Hill estimated the crowd, the majority of them young men wearing "hoodies", at about 300.
The PSNI said it was working to ease tension but did not directly intervene, claiming that no officer witnessed an offence and no complaint had been made.
Senior officers denied they were doing nothing. Chief Supt Henry Irvine said: "I would appeal for calm and would urge those in the community with influence to use that influence. We are very much aware of the concerns of the local community.
"These situations, as we often say, cannot be resolved by police alone. But let me assure you, my officers are on the ground and are working hard to resolve the tensions."
The Irish Times understands that one senior LVF figure was forced from his house in the area on Saturday by others within his organisation. Then the UVF mobilised to force other people thought to be associated with the LVF from their homes.
The UVF presence on the streets has been welcomed by residents, who complained that drug-dealing and other activity was ruining their community.
Progressive Unionist leader David Ervine visited the estate yesterday and condemned the action, saying: "I can't agree with people on the streets like this." However, he added that the dangerous situation arose from a failure by the authorities to act.
"That's why they did it, because no one else would."
Mr Ervine also met Northern Secretary Peter Hain a short distance away at Stormont Castle.
The meeting was ostensibly about the British government's threat to enact further financial sanctions against the PUP over its alleged failure to do enough to halt UVF violence.
Mr Ervine said at the weekend he feared the feud would get worse and that the UVF seemed intent on wiping out its rival.
He also suggested that all talk of a political future for the UVF was on hold. "There was a consultation going on which has stopped. It stopped because they're busy doing other things, it would seem."
There were hopes last night that two intermediaries, the Rev Mervyn Gibson and Sammy Douglas, would attempt to draw both sides into negotiation.
The Independent Monitoring Commission, which reviews the paramilitary ceasefires, is concentrating on loyalist paramilitaries in the run-up to its autumn report. It is expected to report relatively high levels of loyalist violence and criminality when compared to Provisional IRA activity.