(Refiles this June 7 story to correct editing credit.)

KADUNA, Nigeria (Reuters) - A northern Nigerian state’s governor on Wednesday ordered the arrest of activists for demanding the eviction of eastern Igbo people, amid rising tensions between ethnic groups that hark back to the country’s Biafra civil war.

Secessionist feeling has simmered in Nigeria’s east since the Biafra separatist rebellion, a mainly Christian Igbo movement, tipped the country into a civil war from 1967 to 1970 that killed an estimated 1 million people.

Since 2015, those sentiments have heightened, spurred by a lack of economic development and fears of Islamic encroachment, often blamed on the government of Muslim President Muhammadu Buhari. That has in turn sparked ill will toward secessionists, especially from northern Muslims.

“All Igbos currently residing in any part of northern Nigeria are hereby served notice to relocate within three months and all northerners residing in the East are advised likewise,” a spokesman for a movement called the Northern Youth Groups said on Tuesday in the northern city of Kaduna.

He called for “sustained, coordinated campaigns” to remove Igbo people from the region.

The Northern Youth Groups coalition is made up of organizations who claim to promote the interests of the region.

The widespread slaughter 51 years ago of Igbos living in Nigeria’s north helped spur the Biafran secession from 1967-70, which led to war against Nigeria’s central government and a famine in which millions died.

Kaduna Governor Nasir El-Rufai on Tuesday ordered the arrest of the signatories to the Northern Youth Group statement, condemning their “inciting” and “hate speech.”

The Kaduna government “assures every resident of our state that their constitutional and human rights to live peacefully and own property wherever they choose is sacrosanct,” a spokesman for El-Rufai said in a statement.

Nigeria has in recent years seen a rise in other ethno-religious conflicts, particularly deadly clashes between Muslim herders and Christian farmers, partly over land use, in the region known as the Middle Belt.