Bombs and gun battles across Afghanistan killed more than 30 insurgents, five civilians and two NATO coalition service members, officials said today, a round of violence that shows the challenges facing international forces seeking to handover security duties to their local counterparts.Two children were among four civilians killed on Monday in Eastern Paktia province when a bomb ripped through the tractor they were riding on, said Ghulam Dastagir, deputy provincial police chief. In northern Kunduz province, insurgents attacked a checkpoint set up by a local police force, sparking heavy fighting. Two police officers were killed, along with 17 of the attackers, said local Police Chief Mohammad Ayub Haqyar.