Authorities in Bangladesh tightened a nationwide curfew after dozens of people, including at least 13 police officers, were killed in a wave of violence on Sunday. The clashes came a day after protesters called for nationwide “civil disobedience” to demand the ouster of Prime Minister Sheikh Hasina’s government. “The curfew will remain effective until further direction from 6 pm (1200 GMT) at all cities, divisional and district headquarters, municipal areas, industrial zones and towns across Bangladesh,” an order issued by the Ministry of Home Affairs said. The government first imposed a curfe…