At least 20 people were killed and others sustained gunshot wounds on Thursday after armed men attacked two villages in the north central state of Plateau, where violence between cattle herders and farmers is common, police said.

Plateau police spokesperson Alfred Alabo said the attacks took place in the early hours of Thursday when unidentified gunmen stormed Tagwam Lawuru village, shot and killed 17 people before killing another three in nearby Layowok village.

“As a result of the attacks, several other people sustained varying degrees of gunshot injuries,” said Alabo in a statement, urging calm and promising to arrest and prosecute perpetrators.

The violence is often painted as ethno-religious: chiefly Muslim Fulani herders clashing with mainly Christian farmers.

But many experts and politicians say climate change and expanding agriculture are creating competition for land that is pushing the farmers and herders into conflict, regardless of faith or ethnicity, reports Reuters.