Afghan authorities have arrested eight police officers in connection with the deaths of six children in an explosion in the country’s troubled north.The interior ministry said in a statement that the officers were suspected of firing rockets into a pond to catch fish in the Doshi district of northern Baghlan province on Friday. Local Afghan sources say the rockets went astray and killed children who were playing on the other side of the giant pond. Provincial officials say the children were aged between 10 and 14. The United Nation has expressed grave concern over the “unacceptable” and “very worrying” rise in child casualties across Afghanistan. UN Children's Fund (UNICEF) issued a statement in June saying that at least 414 Afghan children were killed or wounded in the first four months of 2013.