MEND spokesman Jomo Gbomo, in a statement e-mailed to Bloomberg News, said a campaign would begin May 31 to "save Christianity in Nigeria."
MEND last week attacked an oil well in Bayelsa state that belonged to Royal Dutch Shell. It ramped up its militancy in the Niger Delta after leader Henry Okah was sentenced last month in South Africa to 24 years in prison on terrorism-related charges.
"The bombings of mosques, hajj camps, Islamic institutions, large congregations in Islamic events and assassinations of clerics who propagate doctrines of hate will form the core mission of this crusade," Gbomo said.
MEND has waged a militant campaign against oil facilities in the Niger Delta region. Several companies, including Shell and Chevron, have joint ventures with the Nigerian National Petroleum Corp.
Gbomo said militants from Boko Haram were called on to stop their campaign against Christians in Nigeria, a country divided along religious lines.
More than 80 percent of the government's revenue comes from crude oil exports.