Five Indo-Tibetan Border Police (ITBP) jawans were killed and several others were seriously injured after a huge boulder fell on their vehicle in Lower Siang in Arunachal Pradesh, district yesterday. The incident occurred when a bus carrying 20 ITBP personnel of 49 Battalion was hit by a huge rock that rolled down a mountain due to monsoon rains on the Basar-Akajan road near Likabali. The bus was on its way to Dibrugarh in Assam from Basar in West Siang district. The seriously injured were shifted to Delhi by a special chopper for treatment.