Twelve persons, including 11 children, were killed on Tuesday when a school bus crashed and burst into flames as it travelled through a tunnel in China's Shandong province, police said.Of the 11 children, who were aged between three and six, five were from South Korea and six Chinese nationals, Xinhua news agency reported. They were all students at an international kindergarten school in Weihai city, the police said.The accident occurred at about 8.59 a.m. inside the Taojiakuang tunnel when the bus was on its way to the school with 13 people onboard, including the children's teacher.The driver also died and the teacher sustained serious injuries.The provincial government has assigned a team to investigate the cause of the accident.