NEW : Four of at least 27 people killed are children , police say . U.N. official Martin Kobler appealed Thursday for security forces to be on `` heightened alert '' so that citizens can vote `` in a safe environment without fear of violence . '' NEW : The building targeted in western Baghdad had an ice cream shop and medical offices . A bomb was hidden in a plastic bag and detonated around 10 p.m. local time . BAGHDAD - MARCH 01:
NEW : Four of at least 27 people killed are children , police say . NEW : The building targeted in western Baghdad had an ice cream shop and medical offices . A bomb was hidden in a plastic bag and detonated around 10 p.m. local time . BAGHDAD - MARCH 01: