North Korean leader Kim Jong Un received a new designation from the ruling Workers' Party on Monday, the last day of the party's first congress in more than 30 years, according to media reports.
Kim Yong Nam, chairman of the presidium of the Supreme People's Assembly, introduced Kim as the party's chairman, a symbolic move meant to officially endorse his leadership, Japanese media reported from Pyongyang.
The new title came four days into the rare gathering, the first in which foreign journalists were allowed inside.
The BBC reported that one of its journalists was expelled from the country along with his team because he had been "speaking very ill of the system" in his reporting.
Reporter Rupert Wingfield-Hayes, producer Maria Byrne and camera operator Matthew Goddard were detained Friday when they were about to leave the isolated communist country.
They remained in Pyongyang over the weekend and flew to Beijing on Monday, the BBC said.
"The North Korean leadership was displeased with their reports highlighting aspects of life in the capital (Pyongyang)," it said, adding that Wingfield-Hayes was interrogated for eight hours and had to sign a statement.
"We are very disappointed that our reporter Rupert Wingfield-Hayes and his team have been deported from North Korea after the government took offence at material he had filed," the broadcaster said.
"Four BBC staff, who were invited to cover the Workers' Party Congress, remain in North Korea and we expect them to be allowed to continue their reporting."
The gathering is seen as a way for Kim to consolidate his position as supreme leader of the secretive nation. As secretary of the group, which runs the one-party state, he was already considered its head.
Foreign journalists visiting North Korea normally have to go through strict vetting procedures, promise to stick to reporting on agreed subjects and pay fixed daily rates in foreign currency for packages of accommodation, organized activities and official chaperones.