A bomb packed with nuts and bolts injured up to 50 young revellers on Friday at a huge outdoor concert in the Belarussian capital Minsk attended by President Alexander Lukashenko, officials said. Interior Minister Vladimir Naumov said a second explosive device that failed to detonate had also been found at the same venue. Lukashenko, who has ruled Belarus since 1994, was at the concert at the time of the blast and visited the site within a few minutes, his press office said. There was no immediate indication of who was responsible for the attack at the Independence Day concert, which occurred at 00:30 am (local time).