The government on Sunday night blocked popular social networking sites Twitter, Skype and Imo.A high official of a mobile phone operator told Jagonews24.com that they received such a letter around 9:00pm.Bangladesh Telecommunication Regulatory Commission (BTRC) on Sunday evening evening sent a letter to all mobile phone operators and telecom service providers in the country, asking them to suspend the three popular services immediately.Earlier on Thursday, the government unblocked Facebook after banning 22days, but the ban on WhatsApp and Viber remains in place.