Kiraithe says attackers of the varsity student and NMG staff will be brought to book.
The government has termed as murder the killing of pregnant Rongo University student Sharon Otieno, whose body was found in a forest in Homa Bay on Wednesday morning.
At the same time, the Uhuru Kenyatta administration condemned the Monday attempted abduction, which it termed as "attempted murder", of Nation reporter Barrack Oduor.
In a statement to newsrooms on Wednesday, Government Spokesman Eric Kiraithe said Sharon died in circumstances that “distinctly point to a murder.”
Mr Kiraithe commended Mr Oduor as a “courageous” man who was trapped in the course of work.
“It now appears that his abduction was an attempted murder,” he said.
He assured the public and the media fraternity that the matter will be expeditiously investigated.
"Perpetrators of this heinous crime will be made to face the full force of the law," the government said.
Mr Kiraithe's statement comes just hours after the body of Sharon, 26, was found dumped in Kodera Forest in Homa Bay County.
The second year student, who was pursuing a degree in Medical Records and Information, has been missing since Monday evening.
Sharon and Mr Oduor were kidnapped moments after being lured out of Graca Hotel in Rongo around 7.35pm by Governor Okoth Obado’s Personal Assistant Michael Oyamo.
Mr Obado has since denied claims linking him to the murder of the student and the attempted abduction of Mr Oduor.