Nigerian politicians have criticized a call to expel members of one of the country’s main ethnic groups from the north of the country, as tensions rise ahead of the 50th anniversary of the Biafran civil war.

The governor of Kaduna State in northern Nigeria said he had ordered the arrest of the leaders of a coalition of group claiming to represent the north’s interests, which on Tuesday issued a statement calling for the expulsion of all Igbos from the north. The Igbo are one of the three largest ethnic groups in Nigeria and are based mostly in the east of the country.

Governor Nasir El-Rufai said that he had ordered police to arrest signatories to the statement, whom he said had sought to “promote their own agenda of hate, division and incitement.”

The call relates back to the Biafran war, which was preceded by the flight of Igbos across Nigeria to their ancestral homelands in the east of the country. On May 30, 1967, a former Nigerian military commander, Odumegwu Ojukwu, declared the annexation of a Republic of Biafra in eastern Nigeria.

The decision sparked a civil war between Nigerian and Biafran forces, which began on July 6, 1967. At least 1 million people were killed during the three-year civil war—many of whom starved to death after Nigeria blockaded Biafra’s borders—and Biafra wentback to being a part of Nigeria in 1970.

Pro-Biafra sentiment has been on the rise in recent years, particularly since the arrest of Nnamdi Kanu, a British-Nigerian who leads the Indigenous People of Biafra (IPOB) group. Nigerian security services arrested Kanu in October 2015, and he was detained for almost two years without trial before being released on bail in May. Kanu is now awaiting trial in Nigeria.

The coalition of activist groups—which calls itself the Northern Youth Groups, according to Reuters —issued a statement on Tuesday in response to recent protests by pro-Biafra groups, including IPOB, which had led to various cities in eastern Nigeria being shut down.

A spokesman for the Northern Youth Groups said that Northerners were “tired of the marriage” of Nigeria’s main ethnic groups and said that the recent IPOB protests were proof that Igbos had “abused the unreciprocated hospitality” offered to them in the north.

“This latest action and similar confrontational conducts, which amount to a brutal encroachment on the rights of those termed as non-indigenous people residing and doing lawful businesses in those areas illegally demarcated and defined as Biafra by the Igbo, are downright unacceptable and shall no longer be tolerated,” said the Northern Youth Groups, in a statement reported by Nigerian e-newspaper The Cable.

The Northern Youth Groups issued a three-month ultimatum for all Igbos to leave northern Nigeria and called on northerners living in eastern Nigeria to retun. The coalition said that, once the ultimatum had passed, “effective, peaceful and safe mop-up of all remnants of the stubborn Igbo that neglect to heed this quit notice shall commence.”

The statement has been condemned by the governors of 19 northern Nigerian states. Kashim Shettima, the governor of Borno State and head of the Northern States Governors Forum, called on Nigerian security agencies to “unearth the faces” behind the statement.

“We totally condemn such irresponsible pronouncements by those groups. We condemn, we disown, and we are totally distancing ourselves from those faceless groups who don’t have the mandate of the people of northern Nigeria to make such loud pronouncements,” said Shettima at a meeting of the forum on Wednesday, Nigeria’s Premium Times reported.

Modern Nigeria was created by the union of northern and southern British protectorates in 1914, and the country retains deep ethnic and religious divisions. The West African country is home to more than 200 ethnicities: Besides the Igbo, the other two largest groups, the Yoruba and Hausa-Fulani, are based in the southwest and north of the country respectively.

Nigeria is also almost equally divided between a mostly Muslim north and a largely Christian south.

Pro-Biafra activists have complained that Igbos have been marginalized by numerous Nigerian governments, including that of President Muhammadu Buhari, a Muslim from the north who fought on the Nigerian side during the Biafran war.

Buhari—who is currently on medical leave in the U.K.—has previously dismissed pro-Biafra sentiment as the work of “some people who were not even born during the war…saying they want to divide Nigeria.”

Vice-President Yemi Osinbajo, a southern Christian who is the acting president in Buhari’s absence, recirculated a statement made in May on Wednesday, in which he said that “no person or group is more important or more entitled than the other” in Nigeria.

.newsweek