According to reports, tempers arose when workers close to Prachanda opposed after a leader from the Bhattarai faction was allowed to address the gathering.
As an upset Bhattarai tried to leave the venue, leaders from the Prachanda faction preventted him. Some irate workers also allegedly threw a chair at Prachanda, but it didn't hit him.
After both leaders exited the venue, the plenum resumed with leaders deciding to allow all factions to have their say.
Though leaders confirmed the 'clash', some senior leaders denied any physical altercation while admitting there was difference among some workers.
The seventh plenum of Unified Communist Party of Nepal (Maoist), the faction that split last month, has been witnessing problems over distribution of funds.