The MDC Alliance on Friday was forced to abandon Harvest House for fear of violence after some youths at the MDC-T headquarters threatened to assault journalists.
Journalists had been invited to a press conference where the Alliance principals announced their support for Nelson Chamisa as the party's substantive leader on Thursday.
Chamisa apologised to the scribes during the briefing, which was eventually held at the Media Centre.
He promised to investigate what happened with a view to putting an end to the violence.
"We are very sorry for what happened," Chamisa said. "I am going to look into it. I think there is a bigger problem than I thought."
Last week, journalists complained about the militant youths who are accused of also targeting senior party leaders for victimisation.