A man was wrestled to the ground after he pointed a gas pistol at an ethnic Turkish party leader delivering a speech at a party caucus in Bulgaria.
Video from Saturday's event in Sofia shows the man climbing the podium where Ahmed Dogan, the leader of the Movement for Rights and Freedoms, was speaking, and pointing the gun at his face.
Mr Dogan struck the man before he could pull the trigger, while other delegates pulled the assailant to the ground. TV footage showed several people punching, kicking and stamping on the man when he was on the ground.
Police arrested him and took him to a hospital. It was not immediately clear how he got past security to enter the hall with nearly 3,000 people attending.
The attacker was identified by police as Oktai Enimehmedov, 25, a Bulgarian national and ethnic Turk from the coastal city of Burgas. He was carrying the pistol and two knives.
A gas pistol is a non-lethal weapon used for self-defence, but experts say when fired from close range it can cause life-threatening injuries.
Interior minister Tsvevtan Tsvetanov said the gunman had a criminal record for drugs possession, robbery and hooliganism.
The liberal MRF party mainly represents ethnic Turks and other Muslims in Bulgaria, who make up 12% of its 7.3-million population.
The conference had to elect a new leader to succeed Mr Dogan, 58, who is one of the Balkan country's most influential political figures. He has been at the helm of the party since founding it in 1990.
Lyutvi Mestan, who was expected to become the new party leader, said "the true reason for the assault was the language of hatred and confrontation".