Barnaba Marial Benjamin was speaking at the sideline of the accident that killed his Public Relation officer at the national ministry of Information, Joseph Gwak, on Sunday night.
He expressed condolences to the aggrieved family and the entire staff of his ministry.
He said the security forces must investigate the accident and identify the cause and degree of the injury that killed Mr Gwak.
Dr Marial warned the citizens and the youth in particular to drive carefully during Christmas, and appealed to South Sudanese to celebrate Christmas in a peaceful manner.
Christmas and New-Year celebrations are usually bad moments for accidents and crime in Juba and other towns.