A tense situation was reported at Sirikotha, the headquarters of the UNP, during a meeting chaired by party leader former Prime Minister Ranil Wickremesinghe.
The meeting was attended by trade union representatives of the party. Party sources said they were members of the Jathika Sewaka Sangamaya.
The meeting came to an abrupt halt when attendees interrupted the proceedings and voiced their grievances.
The UNP is sharply divided over the formation of the Samagi Jana Balawegaya, led by former Opposition Leader Sajith Premadasa. The UNP has warned strict action against party members working with the Samagi Jana Balawegaya.