At least three opposition activists were killed and many other injured Sunday in southern Bangladesh as police opened fire on protesters allegedly violating a ban on demonstrations, police said. "The lawmen opened fire in self-defense as they were attacked by unruly opposition supporters who forcibly occupied a school ground to hold a rally," Mohammad Shahidullah Chowdhury, district police chief told DPA by telephone. He said two activists were killed in Chandipur, some 60 kilometers south of the capital, Dhaka, while several others, including 11 policemen, suffered bullet wounds after opposition supporters fired upon them. One person was killed in neighboring Laxmipur district after police fired rubber bullets to disperse the angry protestors, said police officer Golam Sarwar. Bangladeshi police have banned demonstrations in Dhaka and some other districts for Sunday in response to plans by the ruling Awami League and opposition Bangladesh Nationalist Party (BNP) to hold competing rallies. The opposition has rescheduled Sunday's mass procession through Dhaka for Monday, but still organized countrywide demonstrations Sunday following the announcement of the 18-hour demonstration ban, which went into effect at 6 am (0000 GMT) Sunday. Former premier and BNP head Khaleda Zia called for agitation to mobilize support for the restoration of a system whereby a non-party caretaker administration oversees general elections. The constitutionally mandated programme was scrapped last year by Prime Minister Sheikha Hasina Wazed's government. The provision was introduced in 1996 and has overseen three national elections. Wazed has said her government would strengthen the Election Commission to enable credible elections. The next general election is scheduled for early 2014. The ruling Awami League has also rescheduled its public meeting to Monday to protest what it calls the opposition's conspiracy to unseat the government.