A video showing a reporter being grabbed by security men and hustled away after asking a question of National Front leader Marine Le Pen circulated on the Internet on Thursday amid confusion over the circumstances of the incident.

It was not clear what had happened beforehand in a room at a convention centre where Le Pen was encircled by reporters and camera crews covering her presidential election campaign.

According to the National Front, it was not responsible for the reporter's ejection from the business forum she was visiting.

In the video, the reporter, Paul Larrouturou of TMC satirical show Quotidien, was filmed shouting "Get off me, get off me... what about freedom of the press?" as he was pulled from the room.

Outside, an altercation took place involving the journalist, a cameraman and the security guards.

Senior National Front official David Rachline tweeted on Wednesday that Le Pen's security service was not responsible. "It is the convention centre's security services who took care of that," he added.

That was denied by the Palais des Congres convention centre, which said on Twitter its security service did not work in that area.

Larrouturou said the security guards were from a private company employed by the Salon des Entrepreneurs business show group that was holding the convention.

He said they had expelled him on the orders of a National Front official who was standing nearby.

A spokeswoman for the Salon des Entrepreneurs reached by Reuters said she could not immediately give a comment on the incident.

Le Pen is among the frontrunners in a closely contested election, although opinion polls show her losing by a big margin in a second-round runoff on May 7 to whichever other candidate she might face there.