AT least 30 Nigerian soldiers were killed in an ambush after gunmen attacked a mine in the Shiroro area of Niger state earlier this week, three sources said. The troops were among security forces deployed to search for mine workers, including four Chinese nationals, said to have been kidnapped during the attack on Wednesday. Emmanuel Umar, the commissioner for state security in northwestern Niger, initially said an unknown number of people had been killed during the mine attack in Ajata Aboki village. When the security forces responded to the attack, the gunmen ambushed them and opened fire, killing 30 soldiers…