Three near-simultaneous car bombs exploded in the northern Iraqi city of Kirkuk on Saturday, killing 21 people and wounding 118, a senior police officer and a doctor said.Two of the bombs exploded near buildings under construction that were used as observation positions by security forces, while the third struck the entrance to a market. The bombings come as Iraqi federal and Kurdish security forces battle a jihadist-led militant offensive that was launched in June and has overrun large areas of five provinces.