Election Commission of Pakistan (ECP) has announced schedule for by-elections on twenty-three seats of National Assembly and four provincial assemblies.According to the schedule issued by the election commission today, polling will be held on the 21st of next month.The candidates can file their nomination papers with the returning officers from the 16th to the 18th of this month. 21st of this month has been fixed as the last date for scrutiny of nomination papers.The candidates can withdraw their nomination papers by 29th of this month. On the same day, the revised list of candidates will be issued.The by elections will be held on six seats of National Assembly, twelve seats of Punjab Assembly, two seats each of Khyber Pakhtunkhwa and Balochistan Assemblies and one seat of Sindh Assembly.These seats became vacant under Articles 43(2), 223(3) and (4) of the constitution as well as due to the death of contesting and returned candidates.Source: Radio Pakistan