Police have detained up to 50 Opposition activists, including prominent leaders and newspaper columnists, on charges of suspected anti-state activities. ‘‘They have been arrested under Section 54 of the Criminal Procedure Code for suspected involvement in anti-state activities,’’ a police officer said on Monday.Those detained include former commerce minister Tofael Ahmed, who is also a key leader of the main Opposition Awami League, as well as the party’s social welfare secretary Mukul Bose and its Dhaka organising secretary Sheikh Bazlur Rahman, along with columnist and human rights activist Shahriar Kabir, police said. The Awami League said the arrests of party leaders and workers were designed to destroy the Opposition in the country.Monday was observed as a day of mourning while black flags fluttered a top buildings in the shocked, silent town of Mymenshingh. Police said nearly 60 people were being treated in hospital with some in critical condition. ‘‘Most of the bodies have been received by their families for burial after autopsy at hospitals,’’ a police officer said. Residents of Mymenshingh, 150 km north of Dhaka, plan to hold a joint rally and prayer session on Monday.Many among the panic-stricken population of about half a million wore black badges as a pall of gloom hung over the town. ‘‘We are closed as people have lost their mood for celebration,’’ said Abdul Latif, manager of a restaurant near one of the bombed cinema halls.Most shops and businesses as well as educational institutions were closed even though the three-day public holiday for the Id al-Fitr festival ended on Saturday. PM Begum Khaleda Zia and leaders of the Bangladesh Nationalist Party and the Opposition Awami League visited Mymenshingh on Sunday and vowed resistance against terrorism. Khaleda ordered an investigation into what she called a conspiracy against Bangladesh.Meanwhile, less than two days after serial bomb blasts ripped through cinema halls in Bangladesh, police on Monday recovered nine crude bombs from near the High Court premises here. Police rushed to the Law Commission Office located in the High Court building, less than a kilometre from the Government Secretariat, and recovered nine crude bombs. Police have filed a case but no arrests have been made so far.