A man jumped on the stage and pointed a gun at the leader of Bulgaria's ethnic Turkish party before security guards wrestled him to the ground during a televised conference.
Ahmed Dogan, the long-time leader of the Movement for Rights and Freedoms (MRF), escaped Saturday's attack unscathed, and it was not immediately clear why the attacker had targeted him at the party congress in Sofia.
Television footage showed the man jumping out of the audience and interrupting a speech by Dogan, 58, who has led the party for almost a quarter of a century.
Security guards were seen beating and kicking the attacker.
"Ahmed Dogan is in good health. Everything is under control," Ceyhan Ibrayamov, MRF official, said.
Police said they had arrested a 25-year-old man from the Black Sea town of Burgas who was also carrying two knives.
The liberal MRF party represents ethnic Turks and other Muslims who make up about 12 per cent of Bulgaria's 7.3 million-strong population.
Dogan is seen as one of the Balkan country's most influential political figures. The MRF was a junior partner in the previous Socialist-led cabinet.
In 1996, Andrei Lukanov, former prime minister, was found shot dead near his home in Sofia, though attacks on politicians are rare.