Gunmen with explosives stormed a church in Owo in southwestern Ondo state on June 5, killing 40 worshippers and wounding at least 60 others, in a rare such attack in the usually safer region.
At the weekend, gunmen from a criminal gang kidnapped 36 people after attacking several villages and two churches in northwestern Kaduna state.
Three people were also killed in the attack, according to local officials.
Nigeria is struggling to end a 13-year jihadist insurgency in its northeast, while criminal gangs in the northwest raid villages and kidnap or kill residents despite army operations against them.
“From the tragedy in Owo two weeks ago that shook our nation to its core, to the killings and kidnappings just this weekend in Kaduna State, it is clear that there is a design by wicked people to put the country under religious stress,” Buhari was quoted as saying late Wednesday.
Although no group claimed responsibility for the attacks, Buhari said the assaults were politically motivated by “enemies” seeking to destroy the country’s unity.