Baghdad ( CNN ) -- A bomb exploded on Thursday night in a popular coffee shop in western Baghdad , killing at least 27 people and wounding 51 others , city police officials said . The bomb was hidden in a plastic bag and then put in a cafe in the Iraqi capital 's al-Amriya neighborhood , where it detonated around 10 p.m. ( 3 p.m . ET ) , according to police . They estimated the device contained about two kilograms of highly explosive material . The explosion ripped through the three-story building , which also includes an ice cream parlor on the first floor and medical offices on the second floor . The coffee shop was on the third floor . Most of those killed and hurt were young men , though four children were among the dead , police said . Mostly Sunni Muslims live in the neighborhood , which is surrounded by walls except for one checkpoint staffed by Iraqi soldiers . The violence follows a spate of attacks preceding the country 's provincial elections , set for Saturday . On Wednesday , three people died and 16 were wounded in four explosions in and around Baghdad , according to police . There is concern that the security situation could affect the outcome of the vote , especially if Iraqis do n't participate because of fears that polling stations may come under attack . 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 . '' In the same statement , Kobler -- the special representative in Iraq for the U.N. secretary-general -- stressed that Iraqi leaders must `` collectively endure a transparent and peaceful election , free of intimidation or political interference . '' And he urged Iraqis to vote , casting it as their patriotic duty . `` I am calling on all women and men to cast their ballots for a better future for them and their children , '' Kobler said . `` My appeal goes particularly to young Iraqis , because you are the future of this country . '' CNN 's Mohammed Tawfeeq reported from Baghdad and Greg Botelho wrote this story from Atlanta .
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 . There have been several attacks ahead of Saturday 's provincial elections .