Gunmen have attacked a cattle market in southeast Nigeria, killing eight traders and 51 cows, police said on Thursday, in the latest violence to hit the restive region.

Southeast Nigeria, where separatist agitations are on the rise, has seen a spate of attacks, with more than 130 police and other security personnel killed by gunmen since last year, according to local media tallies.

It was not immediately clear if Tuesday’s attack on the cattle market in Aba in Abia state was linked to separatist violence.

“There was an attack on the cattle market in Aba by unknown gunmen who killed eight traders and 51 cows on Tuesday,” state police spokesman Geoffery Ogbonna told AFP.

He said an investigation was underway to determine the motives. Ogbonna said traders from various parts of the country used and patronized the market.

“It is a new market. The traders were recently relocated to the site and it is patronised by different ethnic groups in Nigeria.”

Ogbonna said no group has claimed responsibility.

Government offices, including prisons and electoral offices, have also been targeted with hundreds of prison inmates freed in recent violence. Authorities have blamed the attacks on the outlawed Indigenous People of Biafra or IPOB movement, which is campaigning for a separate state for the ethnic Igbo people, or its armed wing, known as ESN. IPOB has denied responsibility. 

Separatist movements in Nigeria are particularly sensitive, after a 1967 unilateral declaration of an independent Biafra republic by dissident Igbo army officers sparked a 30-month civil war.

More than one million people died, most of them Igbos, from the impact of conflict, hunger and disease.