An explosion has shattered the offices of an opposition newspaper in Montenegro, which is highly critical of the country's authorities and has been the target of other attacks, officials said Friday. No one was injured in the blast caused by an explosive device which took place shortly before midnight (2300 GMT) on Thursday, police said in a statement, adding that an investigation was under way. Mihailo Jovovic, the editor-in-chief of Vijesti, said the blast caused "serious damage" to the offices. At the time of the attack, Jovovic and 15 journalists were inside. "This is an unprecedented terrorist attack on our newspaper and an assassination attempt on Jovovic," Vijesti manager Zeljko Ivanovic said. The European Union mission in Montenegro called on the authorities "to immediately investigate and prosecute without any delay the perpetrators of this unacceptable attack." Ivanovic said the violence was the "expected epilogue of a years-long campaign" of Montenegrin veteran Prime Minister Milo Djukanovic and his government and party "against independent media and primarily Vijesti." Thursday's blast was the latest in a series of attacks on Vijesti and its journalists, known for its reporting on corruption affairs involving high-ranking politicians. In August, a bomb exploded outside the home of a Vijesti journalist investigating links between authorities and organised crime bosses in northern Montenegro. Vijesti offices were pelted with stones and fire bombs in skirmishes between extremists and the police during the first gay pride march in the capital in October. In March 2012, another Vijesti journalist reporting on illegal cigarettes trade between Montenegro and Kosovo was beaten in front of her house. The attacker was sentenced to nine months in prison, but his motives were not revealed at the trial. Cars belonging to the paper were torched in 2011, while Jovovic himself was beaten by a driver of then Podgorica mayor for reporting on his son's alleged involvement in illegal activities. Montenegro, a tiny Adriatic country of 650,000, began EU accession talks last year.