MUMBAI (AFP) - Seven people were arrested in Mumbai on Friday after activists from a hardline Hindu regional political party ransacked a television stations offices and beat up staff, police and the network said. About 25 men breached security at the Network 18 group premises in Vikhroli, in the east of the city, breaking glass windows with dustbins, overturning chairs and attacking journalists and other staff. Seven people have been arrested. We will keep them in custody and go deep into this matter to find out why and how these things have happened, Mumbai police chief D. Sivanandan said. The Network 18 group operates CNBC-TV18, which is Indias leading business channel, the English-language general news channel CNN-IBN and regional language equivalents, IBN-7 in Hindi, and IBN-Lokmat, in Marathi. The broadcaster said the IBN-7 and IBN-Lokmat newsrooms were targeted by the protesters, who were shouting slogans in support of the Shiv Sena, a local political party that pushes a protectionist regional agenda. The networks website said attackers told employees that they would not tolerate reports criticising Shiv Sena while TV pictures showed a Network 18 outside broadcast van also being targeted in Pune, southeast of Mumbai. Last week, Shiv Senas ageing leader and figurehead Bal Thackeray criticised leading Indian batsman Sachin Tendulkar for saying that he was an Indian first and that Mumbai, his home city, belongs to all Indians. Thackeray and party activists have been fighting often literally for the rights of people from Maharashtra state and promoting the Marathi language against outsiders since the 1960s. Media outlets have been targeted with violence before for criticising the partys methods and ideology. The chief minister of Maharahstra state, Ashok Chavan, told IBN-7: I have told the police to take the strictest action possible against all the people behind it. I assure the media that this will not be tolerated at any cost. Indias Broadcast Editors Association described the incident as an attack on freedom of expression and the handiwork of elements who want to undermine the role of pen, microphone and camera. Such attacks go against the basic tenets of democracy and need to be condemned in the harshest possible terms, it said in a statement.